Pollen tube growth rates were studied in four Gossypium hirsutum genotypes at various temperatures. The genotypes (TM1, T141, T25, T169) were selected on the basis of their different environmental adaptations. Pistils were pollinated after being removed from the plant and incubated four hours before the pollen tubes were measured using fluorescence microscopy. G. hirsutum pollen tube growth rates vary with genotype and temperature. Pollen tubes grew significantly faster at 30.0 C than at 22.0 C. Pollen tubes grown at 35.0 C were faster than those grown at 22.0 C and slower than 30.0 C, but not always significantly. Significant differences were found in pollen tube growth rates between genotypes, most differences occurring at 22.0 C; 30.0 C had the fewest. No single genotype was the slowest at all three temperatures, but TM1 was always among the fastest. When a single type of pollen is grown on styles of different genotype, significant differences in pollen tube growth rate were observed.