Present research aimed to study relative sexual size dimorphism of Centrobolus dubius compared to congenerics. Millipedes illustrated reversed sexual size dimorphism (SSD) as females were larger than males and broke the rule as this dimorphism increased with body size. SSD was calculated in 18 species of the genus Centrobolus and illustrated as a regression. The approximate relative position of C. dubius was shown from measurements taken in South Africa. The average size of C. dubius was 45 X 4.825 mm (n=8) and logged (x/y = 3.0319063). Males were 45 X 4.825 mm (n=4) and females 50.75 X 57.32348 mm (n=4). The SSD index was 1,040266. Log volume measurements were (females/x = 2.43688 mm³ ; males/y = 2.392273 mm³ ). The difference between the correlation coefficients for the species and the genus were not highly significant (ra = 1, rb = 0.85; na = 8, nb = 18; Z = 4.93; P = 0). The mean volume ratio for C. dubius was 1,040266 which did not differ from 1 (t=1.82574; p-value = 0.097855; NS p < .01; n=8). The evidence cannot be used to suggest sexual bimaturism or competition as causal for SSD in C. dubius.