SOUMATI, B. & DICK, M. W., 1989. Biometry of oogonia and oospores of Saprolegniaceae. The distribution of data on the dimensions of oogonia and oospores for modal and near modal classes of oospore number per oogonium in multiovulate Oomycetes has been determined. Thirteen species of Saprolegniaceae have been examined. Two fundamental relationships have been identified: the first relationship is that of common intercept line regression between the oogonium volume and the mean volume of oospores, the second relationship is that of parallel line regression between the oogonium volume and the sum of volumes of oospores. Neither the quality of water nor the cultural temperature had a significant effect on the pattern of the two relationships. The general pattern of these relationships was the same for all species and with all modal classes tested. Achlya species had higher intercepts in the first relationship and lower slopes in the second relationship compared with Saprolegnia species. The species of hoachlya examined occupied a more intermediate position. The fact that the dimensional relationships are significantly different for different classes of oospore number per oogonium means that these statistics must be considered when writing descriptions of species. The use of overall dimensional ranges embracing all oospore number classes may obscure taxonomic discontinuities.