Yersinia spp. (741 strains) were recovered from 81% of 48 surface water samples collected over a 12-month period from four rivers in Matsue, Japan. The precipitation methods with FeCl3 or Kaolin and the cold enrichment method with Peptone-Mannitol-Phosphate buffer solution were used for recovery. Isolates belonged to Yersinia enterocolitica (Ye) (133 strains), Yersinia intermedia (511 strains), Yersinia frederiksenii (57 strains), Yersinia kristensenii (10 strains) and X2-like organisms (30 strains). Thirty colonies of Ye O3 biotype 3 per ml surface water may relate to the drainage containing 2 X 10(4) Ye O3 biotype 3 per ml, from the piggery that raised Ye O3 biotype 3-positive pigs. There was the negative interrelation between the incidence of isolation of Yersinia spp. and the environmental- and water temperatures. This may be the first documentation of isolation of Ye O3 from surface water.