Sexual size dimorphism (SSD) was investigated in the millipede genus Sphaerotherium. Width was extracted from Attems (1928) monograph and used to compare interspecific variation in mean volumes using a geometric morphometric approach. Based on the formula for a sphere (4/3. π. r3), volume was calculated in seven species and an allometric coefficient of 0.7 found. The allometric equation generated for the genus was ŷ = 0.00251X + 57211.22445. Correlation between SSD and body sizes (R = 0.749728; P = 0.00202; n=7) does now reject Rensch’s rule in Sphaerotherium.