diff --git a/src/ModelingToolkit.jl b/src/ModelingToolkit.jl
index 0a785aca2e..766d9d7b2e 100644
--- a/src/ModelingToolkit.jl
+++ b/src/ModelingToolkit.jl
@@ -102,6 +102,20 @@ function states end
 """
 $(TYPEDSIGNATURES)
 
+Get the set of states decorated as inputs for the given system.
+"""
+function inputs end
+
+"""
+$(TYPEDSIGNATURES)
+
+Get the set of states decorated as outputs for the given system.
+"""
+function outputs end
+
+"""
+$(TYPEDSIGNATURES)
+
 Get the set of parameters variables for the given system.
 """
 function parameters end
@@ -173,7 +187,7 @@ export Differential, expand_derivatives, @derivatives
 export Equation, ConstrainedEquation
 export Term, Sym
 export SymScope, LocalScope, ParentScope, GlobalScope
-export independent_variables, independent_variable, states, parameters, equations, controls, observed, structure
+export independent_variables, independent_variable, states, parameters, equations, controls, observed, structure, inputs, outputs
 export structural_simplify
 export DiscreteSystem, DiscreteProblem
 
diff --git a/src/systems/abstractsystem.jl b/src/systems/abstractsystem.jl
index 87a77436af..1b5c68bf19 100644
--- a/src/systems/abstractsystem.jl
+++ b/src/systems/abstractsystem.jl
@@ -392,6 +392,15 @@ function states(sys::AbstractSystem)
            [sts; reduce(vcat,namespace_variables.(systems))])
 end
 
+function inputs(sys::AbstractSystem)
+    [st for st in states(sys) if isinput(st)]
+end
+
+function outputs(sys::AbstractSystem)
+    sts = vcat(states(sys), map(x->x.lhs, observed(sys)))
+    [st for st in sts if isoutput(st)]
+end
+
 function parameters(sys::AbstractSystem)
     ps = get_ps(sys)
     systems = get_systems(sys)