The yield and some of the properties of the phycocolloids extracted from Gracilaria dentata, Hypnea musciformis, H. flagelliformis, Gigartina acicularis and Grateloupia filicina have been studied in relation to the season of harvesting and habitat along the coast of Ghana. All plants gave high yields of phycocolloids over the "dry" season (October -April), and this sometimes extended into the start of the rains. Leaching by heavy rain is suggested as a possible factor responsible for the low yields during much of the "wet" season. A relationship exists between declining yields of phycocolloid and reduction in standing crop of a population of Gracilaria dentata growing on open flat rocks. Bleached plants in such declining populations had almost three times less phycocolloid than unbleached individuals. Young, re-establishing populations of G. dentata gave very high yields, which were often greater than those obtained in more stable populations consisting of plants of mixed ages. Reduced salinity, high turbidity, and sedimentation are possible factors leading to the lowered phycocolloid yields and reduced abundance of plants during the "wet" season at a site near a river mouth.