Recursive Stored Procedure?

How do I call my Stored Procedure recursively:

CREATE PROCEDURE dbo.GetParentIONode
(
@IONodeID int,
@FullNodeAddress char(100) OUTPUT
)

AS
BEGIN
DECLARE @ParentIONodeID int
IF EXISTS (SELECT ParentIONodeID FROM IONodes WHERE IONodeID = @IONodeID)
BEGIN
SET @FullNodeAddress = CAST((SELECT ParentIONodeID FROM IONodes WHERE
IONodeID = @IONodeID) AS VARCHAR) + ' / ' + @FullNodeAddress
--CALL SP Again with @ParentIONodeID and @FullNodeAddress until
ParentIONodeID = NULL
SELECT @FullNodeAddress
END
END
GO