Detached anthers and pollen of pecan [Carya illinoinensis (Wangenh.) C. Koch] were exposed to a range of relative humidities (RH) and/or temperatures to assess the interaction of these environmental factors on pollen dispersal and germination. Dehiscence of anthers was evaluated at selected time intervals following exposure to ≈56%, 33%, 64%, and 97% RH at 10, 21, 27, and 33C in a factorial experiment. Pollen release increased as RH decreased and temperature increased for detached anthers under laboratory conditions and for attached anthers under field conditions. Inhibition of anther dehiscence by high RH could be overcome or minimized with high temperatures and inhibition by low temperatures, in most cases, with low RH. Temperature effects on specific phases in the pollen germination process were evaluated in a sequence of experiments. First, pollen rehydration temperature was varied (3, 15, 29, 33, and 42C) and incubation temperature during tube development kept constant at 25C. After 2 hours of rehydration, tube formation was maximized at 15C and tube length at 29C. Second, all pollen was rehydrated at a constant temperature (25C) and the incubation temperature during tube development varied (3, 15, 29, 33, and 42C). The temperature for maximum tube formation (15C) was different from that for maximum tube length (33C). Morphology of pollen tubes was normal under all rehydration conditions; but, during incubation for pollen tube development, tubes did not develop at 3C and developed abnormally at 42C. The adverse effect on tube development at 3C, but not at 42C, could be reversed by transferring pollen to 25C.