Trends in population densities of Anopheles albimanus Wiedemann were compared in cotton-and noncotton-growing areas during the cotton-spraying season in an area of ca. 100 square kilometers on the Pacific Coast of El Salvador, C.A. adult collections from stables and larval collections from breeding sites throughout the area from July 1977 to March 1979 showed no significant differences (P = 0.05) in the populations from cotton and noncotton areas. Adult densities in both cotton and noncotton areas was slightly reduced early in the spray seasons.