Raw and treated water samples and distribution system water samples were collected in forty-five Canadian municipalities for the analysis of organotin and organolead compounds. After extraction from the water samples organotin and organolead compounds were alkylated with pentylmagnesium bromide and butylmagnesium chloride respectively and analysed by gas chromatography-microwave induced plasma atomic emission spectrometry (GC-AED) using wavelengths specific for tin (326.23 nm) and lead 405.78 nm). The GC-AED system was optimised for trace level analysis, especially for organolead compounds. Organotin compounds, mainly methyltin and butyltin at concentrations up to 22 ng Sn/L and 43.6 ng Sn/L respectively, were detected in distributed water samples from six municipalities. No organotin compounds were detected in raw water samples indicating that the organotin compounds were leaching into the water from some component of the distribution system. One raw water sample contained six organolead compounds at concentrations from 0.5 to 10 ng Pb/L and five raw water and three distributed water samples contained trace levels ( < 0.5 ng Pb/L) of organolead compounds. Due to the lack of authentic standards the identity of the organolead compounds could not be confirmed by gas-chromatography mass-spectrometry.