diff --git a/doc/source/vertex_edge.rst b/doc/source/vertex_edge.rst
index c0078c1e..e85ace14 100644
--- a/doc/source/vertex_edge.rst
+++ b/doc/source/vertex_edge.rst
@@ -4,7 +4,7 @@ Vertices and Edges
 Vertex Types
 -------------
 
-A vertex can be of any Julia type. For example, it can be an integer, a character, or a string. In a simplistic setting where there is no additional information associated with a vertex, it is recommended to use ``Int`` as the vertex type, which would lead to the best performance.
+A vertex can be of any Julia type. For example, it can be an integer, a character, or a string.
 
 This package provides two specific vertex types: ``KeyVertex`` and ``ExVertex``. The definition of ``KeyVertex`` is:
 
@@ -40,14 +40,7 @@ The ``ExVertex`` type implements a ``vertex_index`` function, as
 
     returns the index of the vertex ``v``.
 
-In addition, for integers, we have
-
-.. code-block:: python
-
-    vertex_index(v::Integer) = v
-
-This makes it convenient to use integers as vertices in graphs.
-
+``SimpleGraph`` is a special case where the vertices are of type ``Int`` and store both their index and identity. In all other graphs, ``Int`` vertices are unordered indices.
 
 Edge Types
 -----------
diff --git a/src/adjacency_list.jl b/src/adjacency_list.jl
index f71f0d79..f56c589f 100644
--- a/src/adjacency_list.jl
+++ b/src/adjacency_list.jl
@@ -35,7 +35,6 @@ is_directed(g::GenericAdjacencyList) = g.is_directed
 
 num_vertices(g::GenericAdjacencyList) = length(g.vertices)
 vertices(g::GenericAdjacencyList) = g.vertices
-vertex_index{V<:ProvidedVertexType}(v::V, g::GenericAdjacencyList{V}) = vertex_index(v)
 
 num_edges(g::GenericAdjacencyList) = g.nedges
 
diff --git a/src/common.jl b/src/common.jl
index ebf1a840..cd3b0df4 100644
--- a/src/common.jl
+++ b/src/common.jl
@@ -8,8 +8,6 @@ typealias AttributeDict Dict{UTF8String, Any}
 #
 ################################################
 
-vertex_index(v::Integer) = v
-
 immutable KeyVertex{K}
     index::Int
     key::K
@@ -37,7 +35,10 @@ typealias ProvidedVertexType Union(Integer, KeyVertex, ExVertex)
 
 function vertex_index{V}(v::V, g::AbstractGraph{V})
     @graph_requires g vertex_list
-    return vertex_index(v, vertices(g))
+    if applicable(vertex_index, v)
+        return vertex_index(v)
+    end
+    return vertex_index(v, vertices(g)) # slow linear search
 end
 
 vertex_index(v, vs::AbstractArray) = findfirst(vs, v)
diff --git a/src/edge_list.jl b/src/edge_list.jl
index faf812cf..6f020950 100644
--- a/src/edge_list.jl
+++ b/src/edge_list.jl
@@ -26,7 +26,6 @@ is_directed(g::GenericEdgeList) = g.is_directed
 
 num_vertices(g::GenericEdgeList) = length(g.vertices)
 vertices(g::GenericEdgeList) = g.vertices
-vertex_index{V<:ProvidedVertexType}(v::V, g::GenericEdgeList{V}) = vertex_index(v)
 
 num_edges(g::GenericEdgeList) = length(g.edges)
 edges(g::GenericEdgeList) = g.edges
diff --git a/src/graph.jl b/src/graph.jl
index 47fa6449..136f19cf 100644
--- a/src/graph.jl
+++ b/src/graph.jl
@@ -55,7 +55,8 @@ vertices(g::GenericGraph) = g.vertices
 num_edges(g::GenericGraph) = length(g.edges)
 edges(g::GenericGraph) = g.edges
 
-vertex_index{V<:ProvidedVertexType}(v::V, g::GenericGraph{V}) = vertex_index(v)
+vertex_index(v::Integer, g::SimpleGraph) = (v <= g.vertices[end]? v: 0)
+
 edge_index{V,E}(e::E, g::GenericGraph{V,E}) = edge_index(e)
 
 out_edges{V}(v::V, g::GenericGraph{V}) = g.finclist[vertex_index(v, g)]
@@ -69,6 +70,17 @@ in_neighbors{V}(v::V, g::GenericGraph{V}) = SourceIterator(g, in_edges(v, g))
 
 # mutation
 
+function add_vertex!(g::SimpleGraph)
+    # ensure SimpleGraph indices are consecutive, allowing O(1) indexing
+    v = g.vertices[end] + 1
+    g.vertices = 1:v
+    push!(g.finclist, Int[])
+    push!(g.binclist, Int[])
+    v
+end
+
+@deprecate add_vertex!(g::SimpleGraph,v) add_vertex!(g::SimpleGraph)
+
 function add_vertex!{V}(g::GenericGraph{V}, v::V)
     push!(g.vertices, v)
     push!(g.finclist, Int[])
diff --git a/src/incidence_list.jl b/src/incidence_list.jl
index 72eab6f8..15c84661 100644
--- a/src/incidence_list.jl
+++ b/src/incidence_list.jl
@@ -42,7 +42,6 @@ vertices(g::GenericIncidenceList) = g.vertices
 
 num_edges(g::GenericIncidenceList) = g.nedges
 
-vertex_index{V<:ProvidedVertexType}(v::V, g::GenericIncidenceList{V}) = vertex_index(v)
 edge_index{V,E}(e::E, g::GenericIncidenceList{V,E}) = edge_index(e)
 
 out_edges{V}(v::V, g::GenericIncidenceList{V}) = g.inclist[vertex_index(v, g)]
diff --git a/test/graph.jl b/test/graph.jl
index cae32f5e..2042cd9a 100644
--- a/test/graph.jl
+++ b/test/graph.jl
@@ -10,7 +10,8 @@ using Base.Test
 #
 #################################################
 
-sgd = simple_graph(4)
+sgd = simple_graph(3)
+add_vertex!(sgd)
 
 # concept test