Thank you for your reply. My pool is a 16x32 IG pool with a vinyl liner. The steps are a white plastic. I'm at work right now and don't have access to the results of my water chemistry but all my tests on the water came out normal. I have had my pool for 12 years and don't have any problems with my water. I'm sure the stain came from the chlorine tabs sitting in the basket on top of the steps. I've read elsewhere that you could use muratic acid or rub vitamin C on the stain and it would come off but I haven't tried anything yet. Any suggestions would be very appreciated. Thanks again