Sperm collection methods and the effect of osmolality, ions, sugar, temperature, pH and dilution ratio on sperm motility were investigated in guppies Poecilia reticulata. The present study revealed that the sperm was motile in a wide range of osmolalities (200-470 mOsm kg(-1)) either in Hanks balanced-salt solution (HBSS) or in non-electrolyte solutions such as glucose or sucrose. Sperm collected from crushing testes yielded lower motility and shorter motility duration than samples collected without crushing but gentle disruption. Dilution ratios within the range of 1:50 to 1:500 of sperm to HBSS had minimal effect on sperm motility during extended refrigerated storage. Examination of storage temperature showed that refrigerated storage at 4 degrees C was superior to room temperature (25 degrees C). Sperm was found to tolerate a wide range of pH from 5.6 to 7.8, but motility was affected negatively by pH values >7.8.