Sixteen isolates of Streptomyces were evaluated under field conditions in El-Gemmeiza and Sirs El-Lian in 2006 and 2007 as to their efficiency in suppressing cotton seedling damping-off.  Seeds of cotton cultivar Giza 89 in both locations were treated with starch nitrate broth-based suspension of the Streptomyces isolates at a rate of 10 ml/Kg seeds.  The performance of the isolates in reducing infection or increasing seedcotton yield was inconsistent from one site to another.  Moreover, in the same site, the performance was variable from year to year.  In general, the performance of the isolates was better in Sirs El-Lian compared with El-Gemmeiza.  Of the 16 isolates, isolates Nos. 6 and 8 seems to be promising for commercialization for the following reasons: First, they significantly reduced infection in Sirs El-Lian each year and in El-Gemmeiza in 2006.  Second, they increased seedcotton yield in Sirs El-Lian each year.  Third, in El-Gemmeiza, isolates 8 and 6 increased seedcotton yield in 2006 and 2007, respectively.  Cluster analysis was used to differentiate among the isolates based on variation in their antagonistic patterns.  No obvious relationship was observed between grouping the isolates by cluster analysis and their geographic origins.