The aim of this study was to (i) determine environmental pollution in Słowiński National Park on the basis of Zn, Fe, Ni, Cd and Cr concentrations in Pleurozium schreberi gametophores, (ii) draw a map of heavy metal concentrations in the area and (iii) compare the results with previous reports. Samples of Pleurozium schreberi were collected from 27 locations in Słowiński National Park in 2002. Cd concentration was determined by atomic absorption spectrometry (AAS), and Zn, Fe, Ni and Cr concentrations were determined using neutron activation analysis. The results of our research suggest a reduction of heavy metal contamination in the area of Słowiński National Park over the last 27 years and confirmed that the area is one of the cleanest in Poland and may still serve as a reference background for determining pollution in other areas.