A total of 84 amphibians and reptiles were collected in southern Illinois and cultured for leptospires. All cultures were negative. Sera from 182 specimens were tested, and leptospiral agglutinins were detected in 6 of the 12 species examined. Sera from 18 (26%) of 69 seropositive turtles reacted to Leptospira ballum and 59 (86%) reacted to L. hyos. Inversely, 6 of 9 seropositive snake sera (67%) reacted to L. ballum, but only 1 (11%) reacted to L. hyos. Agglutinins were also detected for L. canicola, L. icterohaemorrhagiae, L. pomona, L. sejroe and L. hardjo. The highest percentage (89.1%) of reactors was in red-eared turtles (Pseudemys scripta elegans). There was no diference in the response of either sex or size classes of the red-eared turtles, although no small turtles were collected. It was postulated that high titers and high reactor rates developed in aquatic turtles in response to continue exposure to water-borne leptospires. In terrestial snakes the mode of infection was probably associated with preying on infected rodents.