A larvoscopic examination of faeces collected from localities inhabited by chamois in the Tatra National Park (TANAP) in 1997 demonstrated the presence of the lung nematodes Muellerius spp. (likely to be M. tenuispiculatus and M. capillaris) and Neostrongylus linearis. The overall prevalence of lung nematodes in chamois herds in TANAP was 48.4% with prevalences of 45.6% and 11.9% for Muellerius spp. and N. linearis, respectively. No significant differences in lung nematode prevalences were observed in the biotopes of TANAP with prevalence values of 44.9% being recorded in the High Tatras and 58.5% in the Belianske Tatras. Individual species were in equal proportion in both biotopes, although N. linearis was significantly less prevalent (11.2–13.8%). The prevalence of lung nematodes in the High Tatras varied from 25.0 to 84.2% within individual localities, while in the Belianske Tatras it was more proportionate (50.0–85.7%). In the High Tatras, the prevalence of lung nematodes in the chamois herds peaked during August, declining to its lowest in October. A similar prevalence was also recorded for Muellerius species, while the minimum prevalence of N. linearis was found in July. In the Belianske Tatras, the prevalence of lung nematodes including both species of Muellerius peaked in July and gradually decreased until October. On the other hand, N. linearis was most prevalent in October. The mean L1 count per gram faeces was low (7.6 ± 13.2 larvae g-1).