Among invertebrates, scorpions possess a relatively unique set of reproductive traits. The interrelationships of these traits may have important implications for life history theory, yet there have been few studies of these traits in scorpions. Our data indicate that larger female Centruroides vittatus produce more offspring and have a higher total litter mass than smaller females. There was, however, no significant relationship between offspring size and female or litter size. Mean offspring mass increased with increases in total litter mass and within litter variation in offspring size (coefficients of variation) decreased with increasing total litter mass. These results suggest that large female scorpions with a larger investment in reproduction produced more offspring that were more uniform in size, but not significantly larger, than small females with less investment. The fractional clutch principle and physiological and functional constraints on size and number of offspring are suggested as possible explanations for the relationships we found among offspring size, variation in offspring size and total investment in offspring in C. vittatus.