Length-weight relationships were estimated for 20 fish species collected during scientific surveys conducted with purse seine and gillnets from January 1993 to March 1994 in the Fatala estuary, Guinea. Sample sizes ranged from 10 (Scomberomorus tritor) to 476 (Parachelon grandisquamis) individuals. Fish length ranged from 5.2 cm fork length (Pomadasys jubelini) to 91.5 cm fork length (Sphyraena afra). The coefficients of determination (r²) varied from 0.951 (Chloroscombrus chrysurus) to 0.995 (Hemichromis fasciatus and Polydactylus quadrifilis). Values of the parameter b in the equation W = aLb, where W is weight (g) and L is length (cm), ranged from 3.0171 (S. afra) to 3.6365 (Pseudotolithus moorii). The growth was allometrically positive for 13 fish species (Hydrocynus forskahlii, Caranx hippos, Caranx senegallus, Ethmalosa fimbriata, Sardinella maderensis, Monodactylus sebae, Neochelon falcipinnis, Parachelon grandisquamis, Galeoides decadactylus, Polydactylus quadrifilis, Pseudotolithus elongatus, Pseudotolithus moorii, Pseudotolithus senegallus) and of isometric type for 7 fish species (Chloroscombrus chrysurus, Hemichromis fasciatus, Tylochromis intermedius, Pomadasys jubelini, Ilisha africana, Scomberomorus tritor, Sphyraena afra). The results presented here improve our knowledge of the life history traits of these 20 fish species. Thus, they will serve as a basis for comparative studies on the biology of fish species in West Africa.