A major factor limiting soybean production in Iowa is parasitism by the soybean cyst nematode, Heterodera glycines. Soybean cyst nematode was identified in Grundy, Mahaska, and Ringgold Counties for the first time in 1996 and is now known to be present in 72 Iowa counties. It is very likely that the nematode is present in many other counties as well, but the nonspecific nature of the aboveground symptoms of soybean cyst nematode damage makes early identification or diagnosis of infestations difficult.