A study was conducted to evaluate the response of sunflower cultivars and plant densities grown in two different growing seasons of northern Tamaulipas. Two sunflower hybrids (De kalb G-l0O and G-f 0l) and two varieties (Rib-77 and Victoria) were evaluated under 3 plant densities: 27,5OO, 47.250 and 62,5O0 plants/ha. In 1994, the planting was in the "late" annual season (P-V) and in 1995 was in the "early" annual season (O-I). The highest yield was obtained during the "early" growing season, 2,170 kg/ha, while the lowest yield was 1,678 kg/ha during "late" season. In both seasons, the hybrids and variety Rib-77 had significantly higher yields than the variety Victoria. At Iow densities, increases in seed weight per head, stem and head diameter, and 100-seed weight were observed.