Ground-based direct sun total ozone measurements made at Toronto between 1960 and 1991 are analyzed. During the 1980s the annual average of total ozone was observed to decrease by about 4.2%. This trend is attributed to a statistically significant decrease of ozone by about 7.0% during the late winter, early spring season. The observed trend is consistent with the mid-latitude northern hemisphere results derived from the revised total ozone mapping spectrometer (TOMS) satellite data. Comparing the seasonal behavior of the 1980s trend with that of fluctuations between 1960 and 1980 indicates that the recent trend is distinct from the previous fluctuations which were presumably due to natural variability. Similar results are found when the analysis is applied to other stations. ¿ American Geophysical Union 1991