This dataset provides results obtained by Health Canada’s Canadian Radiological Monitoring Network (CRMN) for 90Sr activity in milk samples originating from various locations across Canada. More information about the CRMN network can be found on the Health Canada website (see link below). From 1984 to 1993, data was collected from 20 locations. After 1993, routine milk analysis for radio-strontium activity was discontinued for all monitoring stations, except the Ottawa location. The results provided here are 90Sr activity concentrations in units of becquerels per litre (Bq/L). Milk is an important matrix for environmental radioactivity assessment since many radionuclides of health concern exhibit efficient soil to milk uptake pathways. As such, the surveillance of milk provides a very good indication as to the severity of environmental impact following a nuclear event. Strontium-90 (90Sr) is a radionuclide of particular concern because it has a long radiological and biological half-life coupled with a high affinity for incorporation into human bone and teeth. Nuclear weapons testing and nuclear accidents have released such long-lived radionuclides into the atmosphere, which in turn have entered the biological life cycle. Nevertheless, a steady decline in the activity concentration of 90Sr in milk can be seen since most of the nuclear weapon testing was halted in the 1960s. The map shows the approximate sampling location for each monitoring station. Stations are found within the associated location range.