In two consecutive years, seedlings of Norway spruce (Picea abies) were planted in a 50-yr-old Norway spruce forest in limed (3.8 tons CaCO3 ha-1) and control plots. After 6 months they were harvested and the mycorrhizal status of the roots was analysed. Six types of mycorrhiza were distinguished. Three decreased after liming, two increased and one was not affected consistently by the liming. The effects on the total mycorrhizal colonization of the roots were opposite for the two years, indicating that the effects of liming are influenced strongly by other environmental factors. Statistical analysis also revealed pronounced natural variation in space. An inventory of the sporocarp-producing fungi showed that the number of saprotrophic species producing sporocarps was significantly higher in the limed plots whereas the number of ectomycorrhizal species was lower in the limed plots, compared with the control plots. It is concluded that more information is needed concerning the effects of liming on different soil types before any general conclusions can be made about its effects on mycorrhizal colonization.