Two thinning treatments (plants at 10 and 15 cm) were evaluated in FIBERMAX 963, SURE-GROW 125, and CIANO CÓCORIM-92, in the December new sowing date. These treatments were compared with the regional check (plants at 20 cm) and a treatment without thinning. This experiment was carried out in the Yaqui Valley Sonora, Mexico in 1998-99. The experiment was analyzed under a split plot experimental design with eight replications. Significant yield differences between varieties and treatments were observed. FIBERMAX 963 out yielded CIANO CÓCORIM-92 and SURE-GROW 125. The regional thinned check yielded significantly less that the other treatments. The non-thinning treatment had similar yield potential to the 10 and 15-cm treatments. There were no significant effects of population densities on yield components and fiber quality.