Statistical analyses of the interrelationships between body size, dry weight, and number of eggs per gravid female were carried out in Gammarus alinus, Bathyporeia sarsi, Microdeutopus gryllotalpa and Corophium insidiosum sampled in Kiel Bay (western Baltic Sea). In all cases closed correspondence between real andpredicted data was found, if the regressions were expressed as power functions (y = b'.xSUP-m or ln y = ln b'+ m.ln x = b + m.ln x). The exponent m seems to be rather constant in gammaridean amphipods: it is usuallyabout 2.4 to 2.8 in the size-weight regression, 2.7 to 3.6 in the size-egg-number regression, and 1.1. to 1.5 in the weight-egg-number regression. The parameter b is obviously more species-dependent and presumably also influenced to a higher degree by ecological factors.