Tissue-specific lead accumulation rates were determined in the estuarine teleost fish, Gillichthys mirabilis, as a function of four variables; sea water lead concentration, duration of exposure to lead, salinity, and temperature. Distinct tissue-specific accumulation rates were found. Spleen, gills, fins, and intestine accumulated the greatest amounts of lead; liver and muscle accumulated the least lead. Decay of lead from tissues of lead-exposed fish was observed only for gills, fins, and intestine, tissues which all possess an outer or inner covering of mucus. Our data suggest that the rapid turnover of lead in these mucus-covered tissues is a result of lead complexing with mucus and subsequent loss of lead when the mucus layer is sloughed off. In spleen and vertebrae, lead levels continued to rise in fish returned to natural (unspiked) sea water from lead-spiked sea water. The rate of lead accumulation was dependent on both the holding salinity and the temperature. Fish held at high temperature accumulated lead more rapidly than fish held at low temperature. The rate of lead accumulation was inversely proportional to the salinity of the medium. Both of these environmental effects on lead accumlation rates could be significant in estaurine habitats where lead concentrations, salinity, and temperature are all apt to vary seasonally.