The effect of various surfactants on the absorption of antipyrine was studied using goldfish and rat. The results are as follows. The threshold concentration of antipyrine was reduced by various surfactants. Overturn time and death time of goldfish, in solution containing different concentration of antipyrine were reduced by the presence of various surfactants. Plots of reciprocal death time versus antipyrine concentration were linear with a positive concentration intercept such as minimum effective concentration. The absorption of antipyrine from rat small intestine was increased by administration with surfactants. As results, is believed to be one of rendering the goldfish membrane or rat small intestine more permeable to antipyrine.