Eleven drinking water treatment plants, located downstream of textile plants or pulp and paper mills, have been sampled monthly during a year for the analysis of 17 nonylphenol ethoxylates (NP1–17EO) and two nonylphenoxycarboxylic acids (NP1–2EC). At all but one plant, results in the drinking water, for the sum of these 19 substances, range between below detection levels and 6.7 μg/l. Annual means are between 0.02 and 2.8 μg/l. At the other plant, the yearly average concentration is 10.4 μg/l and the monthly maximum is 43.3 μg/l. In the surface (pre-treatment) water, the annual mean concentrations of the 11 plants range between 0.14 and 17.8 μg/l and the recorded instantaneous maximum is 55.3 μg/l. According to Canadian health authorities, drinking water is a negligible route of human exposure to nonylphenolic compounds, even at the highest concentrations found in this study. After transformation of the data into nonylphenol equivalents, about 20% of the surface water samples exceed the Canadian 1 μg/l nonylphenol water quality guideline for the protection of aquatic life. Some results also exceed Québec's 6 μg/l nonylphenol guideline. The efficiency of the plants in removing nonylphenolic compounds from drinking water is highly variable, ranging from 11% to 99%.