Intraperitoneal injection of goldfish with Thioglycollate induced an acute peritoneal inflammation connected with an influx of leucocytes. The number and some properties (migratory activity, PMA-induced chemiluminescence) of leucocytes were analysed in parallel in suspensions of peritoneal and head kidney (HK) leucocytes. It was found that the increased number of peritoneal large granular cells corresponds with the decreased number of such leucocytes in HK. Moreover, the enhancement of migratory and chemiluminescent activity of peritoneal leucocytes corresponds with the inhibition of these activities in head kidney cells. The results strongly indicate that the head kidney, the major lymphomyeloid organ of teleosts, is the main source of leucocytes inhabiting the peritoneal cavity following induction of an acute inflammation.