The response of three new cotton varieties to application of thidiazuron was evaluated through a field research established in Coahuila, Mexico. Main plot was three cultivars; sub plot was application date and sub sub plot was defoliation treatments. Number of leaves and bolls, open bolls percent after application, also cotton yield and fiber quality were evaluated. Seven days after treatment, leaf drop was better with the application of thidiazuron at 125 days after sowing (das), also bolls number was 46% less compared with the treatment at 118 das. Bolls opening at 14 days after treatment was 81 and 72% in the treatments applied at 125 and 118 das. The cotton yield was not affected by application timing of thidiazuron. The fiber length was the quality component affected in the new varieties of cotton.