The response of three new cotton varieties to Thidiazuron application was evaluated in a field research conducted during the 1995 cotton growing season at Matamoros, Coahuila, Mexico. The experimental design was a randomized complete block with split-splot arrangement and four replications. Number of leaves, percent of open bolls after application, cotton yield, and fiber quality were evaluated. Leaf drop was superior with the Thidiazuron application at 125. Open bolls at 14 days after treatment was 81 and 72% in the treatments applied at 125 and 118 days after planting respectively. The cotton yield was not affected by application date of Thidiazuron. The fiber length was the fiber quality component affected in the new cotton varieties.