We apologize for the lateness of our reply. Having lived in Thurston County myself, I understand the frustration of moss in the lawn. You are probably killing the existing moss, but if the underlying problem isn't corrected, then you will keep having this problem. The answer is encouraging thick, healthy grass. Some underlying problems that cause poor grass growth can be: - wrong type of grass for your climate - compacted soil - inadequate drainage - thatch There are several ways to improve these conditions. - Use your moss control in late winter and early spring - Dethatch and aerate your soil - Over dress with a mixture turftype rye grasses or ryegrass/fescue blend and/or also top dress with 1/4 inch of topsoil. Keep the soil moist until the seedlings are established. I have included a couple information sheets for you to browse through also, for more information if you are interested. http://gardening.wsu.edu/library/lawn003/lawn003.htm http://cru.cahe.wsu.edu/CEPublications/eb0482/eb0482.pdf Great question. Good luck.