diff --git a/app/src/main/java/com/annimon/hotarufx/exceptions/HotaruRuntimeException.java b/app/src/main/java/com/annimon/hotarufx/exceptions/HotaruRuntimeException.java
new file mode 100644
index 0000000..5bb76c8
--- /dev/null
+++ b/app/src/main/java/com/annimon/hotarufx/exceptions/HotaruRuntimeException.java
@@ -0,0 +1,14 @@
+package com.annimon.hotarufx.exceptions;
+
+import com.annimon.hotarufx.lexer.SourcePosition;
+
+public class HotaruRuntimeException extends RuntimeException {
+
+    public HotaruRuntimeException(String s) {
+        super(s);
+    }
+
+    public HotaruRuntimeException(String string, SourcePosition start, SourcePosition end) {
+        super(string + " at " + start + " .. " + end);
+    }
+}
\ No newline at end of file
diff --git a/app/src/main/java/com/annimon/hotarufx/exceptions/VariableNotFoundException.java b/app/src/main/java/com/annimon/hotarufx/exceptions/VariableNotFoundException.java
new file mode 100644
index 0000000..81dd64f
--- /dev/null
+++ b/app/src/main/java/com/annimon/hotarufx/exceptions/VariableNotFoundException.java
@@ -0,0 +1,10 @@
+package com.annimon.hotarufx.exceptions;
+
+import com.annimon.hotarufx.lexer.SourcePosition;
+
+public class VariableNotFoundException extends HotaruRuntimeException {
+
+    public VariableNotFoundException(String variable, SourcePosition start, SourcePosition end) {
+        super("Variable " + variable + " does not exists", start, end);
+    }
+}
diff --git a/app/src/main/java/com/annimon/hotarufx/parser/visitors/InterpreterVisitor.java b/app/src/main/java/com/annimon/hotarufx/parser/visitors/InterpreterVisitor.java
index ac348fa..8f00354 100644
--- a/app/src/main/java/com/annimon/hotarufx/parser/visitors/InterpreterVisitor.java
+++ b/app/src/main/java/com/annimon/hotarufx/parser/visitors/InterpreterVisitor.java
@@ -1,9 +1,11 @@
 package com.annimon.hotarufx.parser.visitors;
 
+import com.annimon.hotarufx.exceptions.VariableNotFoundException;
 import com.annimon.hotarufx.lib.Context;
 import com.annimon.hotarufx.lib.NumberValue;
 import com.annimon.hotarufx.lib.Value;
 import com.annimon.hotarufx.parser.ast.*;
+import lombok.val;
 
 public class InterpreterVisitor implements ResultVisitor<Value, Context> {
 
@@ -14,12 +16,17 @@ public class InterpreterVisitor implements ResultVisitor<Value, Context> {
 
     @Override
     public Value visit(AssignNode node, Context context) {
-        return NumberValue.ZERO;
+        val value = node.value.accept(this, context);
+        return node.target.set(this, value, context);
     }
 
     @Override
     public Value visit(BlockNode node, Context context) {
-        return NumberValue.ZERO;
+        Value last = NumberValue.ZERO;
+        for (Node statement : node.statements) {
+            last = statement.accept(this, context);
+        }
+        return last;
     }
 
     @Override
@@ -39,11 +46,35 @@ public class InterpreterVisitor implements ResultVisitor<Value, Context> {
 
     @Override
     public Value visit(ValueNode node, Context context) {
-        return NumberValue.ZERO;
+        return node.value;
     }
 
     @Override
     public Value visit(VariableNode node, Context context) {
-        return NumberValue.ZERO;
+        return node.get(this, context);
+    }
+
+    @Override
+    public Value get(AccessNode node, Context context) {
+        return null;
+    }
+
+    @Override
+    public Value set(AccessNode node, Value value, Context context) {
+        return null;
+    }
+
+    @Override
+    public Value get(VariableNode node, Context context) {
+        val result = context.variables().get(node.name);
+        if (result == null)
+            throw new VariableNotFoundException(node.name, node.start(), node.end());
+        return result;
+    }
+
+    @Override
+    public Value set(VariableNode node, Value value, Context context) {
+        context.variables().put(node.name, value);
+        return value;
     }
 }
diff --git a/app/src/test/java/com/annimon/hotarufx/parser/visitors/InterpreterVisitorTest.java b/app/src/test/java/com/annimon/hotarufx/parser/visitors/InterpreterVisitorTest.java
new file mode 100644
index 0000000..fda1779
--- /dev/null
+++ b/app/src/test/java/com/annimon/hotarufx/parser/visitors/InterpreterVisitorTest.java
@@ -0,0 +1,46 @@
+package com.annimon.hotarufx.parser.visitors;
+
+import com.annimon.hotarufx.exceptions.VariableNotFoundException;
+import com.annimon.hotarufx.lexer.HotaruLexer;
+import com.annimon.hotarufx.lib.Context;
+import com.annimon.hotarufx.lib.NumberValue;
+import com.annimon.hotarufx.lib.Value;
+import com.annimon.hotarufx.parser.HotaruParser;
+import org.junit.jupiter.api.Test;
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.allOf;
+import static org.hamcrest.Matchers.hasEntry;
+import static org.hamcrest.Matchers.is;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+class InterpreterVisitorTest {
+
+    static Value eval(String input) {
+        return eval(input, new Context());
+    }
+
+    static Value eval(String input, Context context) {
+        return HotaruParser.parse(HotaruLexer.tokenize(input))
+                .accept(new InterpreterVisitor(), context);
+    }
+
+    @Test
+    void testAssignVariables() {
+        Context context = new Context();
+
+        String input = "A = 1\nB = 2\nC = B";
+        Value result = eval(input, context);
+
+        assertThat(result.toString(), is("2"));
+        assertThat(context.variables(), allOf(
+                hasEntry("A", NumberValue.of(1)),
+                hasEntry("B", NumberValue.of(2)),
+                hasEntry("C", NumberValue.of(2))
+        ));
+    }
+
+    @Test
+    void testRuntimeErrors() {
+        assertThrows(VariableNotFoundException.class, () -> eval("A = B"));
+    }
+}
\ No newline at end of file