Residues of oxolinic acid in Penaeus monodon weighing 10-12 gm were examined after force-feeding at levels of 10,20 and 30 mg/kg body weight respectively. Seven days after the feeding experiment, residues of oxolinic acid in hepatopancreas, haemolymph and muscle varied depending on the dose given. The maximum level was detected in the hepatopancreas. However, over a long period the concentration of oxolinic acid in the three tissues decreased gradually and were not significantly different. The residence time of oxolinic acid in hepatopancreas, haemolymph and muscle after force-feeding with the dose of 10mg/kg were 27 days, 10 days and 7 days respectively. Levels of oxolinic acid were measured after and oral dose of 20 mg/kg body weight was given as medicated feed for 7 days and 10 days. The concentration of oxolinic acid residues in all three tissues examined for both experiments wer not significantly different. The residence time of oxolinic acid in the hepatopancreas after 10 and 7 days of feeding with medicated pellets was 38 days and 33 days respectively

in the muscle this was 17 days and 20 days respectively

and in the haemolymph was 5 days for both experiments.