Phytoplankton abundances and accompanying morphometric, physical, and chemical data from 95 Labrador lakes were subjected to statistical analysis to determine the structure of the phytoplankton communities and to relate environmental factors to the patterns observed. Factor analysis of the 22 measured physical and chemical variables reduced the data to six derived environmental factors: hardness, dystrophy, lake size, salinity, oligotrophy, and seasonality. The analysis showed that the low-pH lakes are associated with dystrophy and hence are likely to be naturally acidic. There was no evidence of anthropogenic acidification. Eight groups of co-occurring taxa were recognized from the data set, and all but two exhibited relatively consistent habitat preferences. It was suggested that the groups represent "species associations" in the sense that each group contains taxa that occur together because of similar requirements for a specific set of environmental conditions. Several lake types were identified as potentially influencing the distribution of phytoplankton in Labrador: small, dystrophic lakes; clear, softwater lakes; clear, hardwater lakes; large, hardwater lakes; and coloured, hardwater lakes.