diff --git a/M6502/M6502.Symbols/Parser.cs b/M6502/M6502.Symbols/Parser.cs
index dce0ef6..0d0455f 100644
--- a/M6502/M6502.Symbols/Parser.cs
+++ b/M6502/M6502.Symbols/Parser.cs
@@ -32,25 +32,41 @@
                 public List<Symbol> Labels { get; } = [];
                 public List<Symbol> Equates { get; } = [];
 
+                // Value lookup structures
+                public Dictionary<int, List<Symbol>> Addresses { get; } = [];
+                public Dictionary<int, List<Symbol>> Constants { get; } = [];
+
                 #endregion
 
                 #region Lookups
 
                 #region Label lookup
 
-                public List<Symbol> LookupLabels(int address)
+                public void AddLabel(Symbol symbol)
                 {
-                    var returned = new List<Symbol>();
-                    foreach (var label in this.Labels)
+                    if (symbol.Type != "lab")
                     {
-                        if (label.Value == address)
-                        {
-                            returned.Add(label);
-                        }
+                        throw new ArgumentOutOfRangeException(nameof(symbol), "Not a label");
                     }
-                    return returned;
+                    this.Labels.Add(symbol);
+                    this.AddAddress(symbol);
                 }
 
+                private void AddAddress(Symbol symbol)
+                {
+                    var value = symbol.Value;
+                    if (this.Addresses.TryGetValue(value, out var symbols))
+                    {
+                        symbols.Add(symbol);
+                    }
+                    else
+                    {
+                        this.Addresses.Add(value, [symbol]);
+                    }
+                }
+
+                public List<Symbol> LookupLabels(int address) => this.Addresses.TryGetValue(address, out var symbols) ? symbols : [];
+
                 public Symbol? LookupLabel(int address)
                 {
                     var labels = this.LookupLabels(address);
@@ -80,19 +96,31 @@
 
                 #region Constant lookup
 
-                public List<Symbol> LookupEquates(int constant)
+                public void AddEquate(Symbol symbol)
                 {
-                    var returned = new List<Symbol>();
-                    foreach (var equate in this.Equates)
+                    if (symbol.Type != "equ")
                     {
-                        if (equate.Value == constant)
-                        {
-                            returned.Add(equate);
-                        }
+                        throw new ArgumentOutOfRangeException(nameof(symbol), "Not an equate");
                     }
-                    return returned;
+                    this.Equates.Add(symbol);
+                    this.AddConstant(symbol);
                 }
 
+                private void AddConstant(Symbol symbol)
+                {
+                    var value = symbol.Value;
+                    if (this.Constants.TryGetValue(value, out var symbols))
+                    {
+                        symbols.Add(symbol);
+                    }
+                    else
+                    {
+                        this.Constants.Add(value, [symbol]);
+                    }
+                }
+
+                public List<Symbol> LookupEquates(int constant) => this.Constants.TryGetValue(constant, out var symbols) ? symbols : [];
+
                 public Symbol? LookupEquate(int constant)
                 {
                     var equates = this.LookupEquates(constant);
diff --git a/M6502/M6502.Symbols/Symbol.cs b/M6502/M6502.Symbols/Symbol.cs
index b1ccc80..d390378 100644
--- a/M6502/M6502.Symbols/Symbol.cs
+++ b/M6502/M6502.Symbols/Symbol.cs
@@ -42,11 +42,12 @@
                     base.Parse(parent, entries);
                     if (this.Type is "lab")
                     {
-                        this._parent.Labels.Add(this);
+                        this._parent?.AddLabel(this);
+
                     }
                     else if (this.Type is "equ")
                     {
-                        this._parent.Equates.Add(this);
+                        this._parent?.AddEquate(this);
                     }
                     else
                     {