The effect of exposure of juvenile individuals of Lymnaea stagnalis to infectious eggs of Opisthioglyphe ranae on dynamics of their growth was investigated under controlled conditions in laboratory. In infected snails enlargement of body weight and linear parameters of shell were observed. Any differences in shell shape, analysed on the base of regression of shell width towards to its height, were not ascertained in uninfected snails and those infected with parthenites of the trematode. The findings with this host-parasite system are discussed in relation to possible mechanisms of pathogenesis of somatic gigantism in other trematode-snail interactions.