This study investigates some short-term effects (5 weeks) of calcium, added to the forest floor, upon the local terrestrial snail populations. Shell sand (400 g/0.25 m(2)) was added in a natural nemoral mixed oak forest near Kristiansand, southern Norway. The results show a significant increase in both individual (from 144 to 355) and species (from 13 to 17) numbers of snails per 0.25 m(2) during the experiment. No significant change occurred in the controls (from 203 to 136 and from 14 to 9, respectively), even though the data suggest a reduction in numbers. Soil samples for chemical analysis were also taken. Positive correlations between snail abundance and amount of calcium, pH-values, and soil base saturation were evident, whereas a negative correlation with amount of phosphorus could be seen. We conclude that addition of calcium to the forest flour in these woods will change the chemical composition of the litter layer and increase the direct availability of calcium to the snails.