Seventy-two forested lake catchments were studied in Quebec (Canada) to examine the influence of climate, atmospheric deposition and catchment characteristics on base cation (BC) concentrations in lake waters (BC C ) and base cation budgets at the catchment scale (BC Q ). The catchments are located along a bioclimatic gradient in a vast (180000km 2 ) study area underlained by the Canadian Shield. Multivariate statistical approaches are used to simultaneously assess the effects of multiple environmental factors on cation fluxes. Mean annual BC C were 132, 40, 24 and 7μmol c l −1 for Ca, Mg, Na and K, respectively. Mean annual BC Q estimates showed exports of 0.826, 0.251, 0.135 and 0.043kmol c ha −1 an −1 for Ca, Mg, Na and K, respectively. There were strong similarities in the spatial variation of BC C and BC Q , and also in their links with environmental factors. We hypothesized that the spatial variability of both, BC C and BC Q , were strongly influenced by the spatial variability in the rates of mineral weathering reactions. Variance partitioning indicated that climate-related effects accounted for 51.6% and 52.7% of the variation in BC Q and BC C , respectively. Nonetheless, lake/catchment morphometry and variables linked to solutes sources (lithology, atmospheric deposition and soil properties) were also included in some models. Overall, BC C and BC Q were positively affected by temperature, precipitation as rain and sulphate depositions, and negatively influenced by precipitation as snow and the number of frost days. Multivariate models explaining up to 69% of variation in BC C and BC Q were developed. This study shows the strong impact of climatic drivers on base cation budgets and, thus, on mineral weathering at the regional scale on the Canadian Shield.