In May 1996, 164 pooled and single samples containing 913 larvae, nymphs and adults of Ixodes ricinus from urban, suburban and wooded biotopes of southern Poland were examined for the presence of Borrelia burgdorferi sensu lato. Ticks were collected by dragging a flag over the vegetation and B. burgdorferi was detected in pooled tick samples by darkfield microscopy or isolated by cultivation in BSK-II medium. Minimum infection rates of nymphs, males and females in the area were 8.2, 9.8 and 10.3%, respectively. Infection of adult I. ricinus ticks on 10 localities fluctuated from 4.0 to 15.0% and over 10% of adult ticks in forests and in some urban and suburban parks of the city Katowice were infected. Five Borrelia strains were isolated from the adult I. ricinus ticks. Relative density of ticks ranged from 20-65 ticks per one collecting hour and from 3.3-10.8 ticks per 100 m², respectively. Frequent occurrence of ticks was also observed in urban parks and residential districts of the city Katowice. The results refer to the risk of human and animal infections by borreliae in the areas of big cities in southern Poland.