For the first time soil solarization was investigated in Croatia both in the field and in the greenhouse in 1991, 1992, 1993 and 1994. For two months (July and August), the soil was mulched with transparent polyethylene (PE) sheets of 0.015 or 0.050 mm thickness. Soil temperatures at depths of 5, 10 and 20 cm were recorded daily. In order to assess nematode population densities, soil samples were analysed before mulching and at the end of the mulching treatment. The results of these experiments showed that soil solarization drastically reduced the population of plant-parasitic nematodes ( Meloidogyne , Pratylenchus , Paratylenchus , Tylenchus , Tylenchorhynchus spp.) by about 97–100 % at a depth of 10 cm and 92–97 % at a depth of 20 cm in the field, while in the greenhouse, the population of plant-parasitic nematodes was reduced by about 89–100 % at a depth of 10 cm and 98–100 % at a depth of 20 cm.In the same experiments, the population of saprophytic nematodes in the field was reduced by about 86–90 % at a depth of 10 cm and 72–89 % at a depth of 20 cm. In the greenhouse, the population of saprophytic nematodes was reduced by about 87–97 % at a depth of 10 cm and 87–93 % at a depth of 20 cm. This data shows that soil solarization was less effective in the control of saprophytic nematodes, which is considered to be an advantage.