Stable isotopic compositions and concentrations of total sedimentary sulphur (S) were determined in cores from 6 lakes in the acid-sensitive Muskoka-Haliburton region of south-central Ontario. The isotopic composition of S in deep sediment (> ∼20 cm) was approximately constant in all lakes, and indicated a pre-industrial δ 34 S value between +4.0 and +5.3‰, which is similar to current bulk deposition. Similarly, total S concentrations in deep sediment were relatively low (1.9-5 mg S g -1 dwt) and approximately constant with depth within cores. All lakes exhibited up-core increases in total S and decreases in δ 34 S at a depth corresponding to the beginning of industrialization in the Great Lakes region (∼1900), resulting in a generally reciprocal depth pattern between total S concentration and δ 34 S ratios. While initial shifts in total S and δ 34 S were likely due to enhanced SO 4 reduction of newly available anthropogenic SO 4 , both the magnitude and pattern of up-core S enrichment and shifts in δ 34 S varied greatly among lakes, and did not match changes in S deposition post 1900. Differences between lakes in total S and δ 34 S were not related to any single hydrologic (e.g., residence time) or physical (e.g., catchment-area-to-lake area ratio) lake characteristic. This work indicates that sediment cores do not provide consistent records of changes in post-industrial S deposition in this region, likely due to redox-related mobility of S in upper sediment. © Springer 2006.