In 2005 and 2006, Ixodes ricinus ticks were collected on two slag (waste rock) heaps from coal mines in the Ostrava area (North Moravia/Silesia, Czech Republic), Oskar (site A) and Emma (site B), partially covered by vegetation including trees, and at a control forest site near Hlucín (site C). The mean numbers of L. ricinus nymphs and imagoes flagged per person-hour were high: 35.3 nymphs and 12.7 imagoes, at site A, 23.3 and 26.0, respectively, at site B, and 25.4 and 16.8, respectively, at control site C. Using dark-field microscopy, 100 nymphs and 100 imagoes (50 females and 50 males) from each site were examined for borreliae. The mean prevalence rates of Borrelia burgdorferi sensu lato in nymphs and imagoes were 10.0% and 12.0%, respectively, at site A, 10.0% and 24.0%, respectively, at site B, and 13.0% and 17.0%, respectively, at site C. Differences in the prevalence of borreliae in nymphal and adult ticks from the slag heaps and control site were insignificant, but adult ticks from site B compared to site A contained borreliae significantly more frequently. The mean numbers of nymphs and imagoes infected with borreliae flagged per person-hour were 3.3 and 1.2, respectively at site A, 1.5 and 2.9, respectively, at site B, and 3.1 and 2.6, respectively, at site C. Isolation experiments for borreliae were carried out only in 16 ticks containing higher numbers of borreliae, with eight of these being culture-positive. The cultured borreliae were identified by PCR-RFLP as B. garinii (3 isolates: two from site B, one from site C), B. afzelii (4 isolates: one from site A, three from site B) and B. burgdorferi s.s. (one isolate from site A). Surprisingly, the results suggest that slag heaps, when covered by woody vegetation and frequented by humans, could theoretically pose roughly the same LB transmission risk to humans as common forest biotopes.