the condition factor is a parameter which acts as a general indicator of the "well-being" of a species, and it can be obtained through the analysis of width vs. weight relationships. the present work aims to investigate size vs. weight relationship and the condition factor of the crab goniopsis cruentata (latreille, 1803). the study area was the mundaú/manguaba estuarine complex, maceió, state of alagoas, northeast brazil. samplings were monthly accomplished from august 2007 to july 2008. a total of 626 individuals were analyzed, being 309 males and 317 females. males were larger and heavier than females, what is expected in many brachyuran. the growth was positive allometric to both males (b = 3.42) and females (b = 3.30), not obeying the "cube law". the condition factor of female was higher than that of male crabs, probably due to the gonad weight of females. it also varied seasonally for both sexes, being higher in the autumn and winter in males, and in the autumn and spring in females, and related to the molt and period of spawning intensification.