The importance of cotton in Mexico is based on cultivated area, high demand for direct and indirect labor, and income generated from export fiber and other secondary products. One factor limiting this crop is the lack of information on local technology to produce high quality seed for commercial purposes. The objective of this research was to determine the effect of plant density and harvest date on yield and quality of cotton seed at La Laguna Experiment Station. Which belongs to the National Institute of Forestry Agriculture and Livestock Research (INIFAP). The results indicate that late harvesting (158 days after seeding) had the best seed yield (366.5 Kg/ha), but also less seed vigor and germination (higher numbers of abnormal and dead seeds) when compared to earlier harvests (127 and 152 days after seeding). The number of abnormal seeds was less at higher plant densities.