Changes in protein synthesis in leaf tissue of six cotton cultivars were studied by comparing the heat-shock protein patterns synthesized at different heat treatments. Leaf tissue responded to thermotolerance treatments by synthesizing a specific set of proteins for each treatment and cultivar, which differed from profiles observed with a direct shift to high temperatures. We found minor differences in the heat-shock proteins profile observed in the prolonged heat treatment when compared with the direct-shift treatment profiles. Newly synthesized proteins of 35 kDa, 37 kDa and 23 kDa were found respectively in Delta Pine Acala 90, Acala 1517–70 and Selati. The late heat-shock protein profiles differed from patterns found with thermotolerance.