Sorghum (Sorghum bicolor [L.] Moench.) research activities at the Tropical Agriculture Research Station (TARS), Mayaguez, Puerto Rico, are described. In cooperation with the Texas Agricultural Experiment Station, 423 daylength insensitive lines from the Sorghum Conversion Program were developed. Numerous new collections were evaluated and classified. Other activities include the evaluation of new cytoplasms and their reactions when crossed to converted lines, the evaluation of grain and forage hybrids, the comparison of daylength sensitive versus daylength insensitive forage hybrids and the development of single and three-way hybrids. Newly developed single and three-way forage hybrids yield over 25 tons ha-1 of dry forage in 180 days. Sorghum populations developed, or in process of development, at TARS in cooperation with other scientists include: 1. populations with reduced hydrocyanic acid (HCN) potential; 2. populations of high yield potential; and 3. populations with increased resistance to common tropical diseases of sorghum.