The experiment on adult Roman snails (Helix pomatia L.) and their offspring showed a positive correlation between the mean egg size and the parent body size. There was no correlation between the parent size and the number of eggs. A trade-off between the egg size and the clutch size was observed. The body size of juveniles at early growth stages was correlated with the parent size; later (offspring aged 2 and 3 months) there was no such correlation, suggesting maternal effect. The results are relevant to estimating the reproductive success and offspring survival rate at early stages.