The occurrence of 25 drug target residues (illicit drugs or pharmaceutically active compounds) was investigated during 85 consecutive days in the influents of a wastewater treatment plant in the Region Centre-Val de Loire, France. This long tracking period allowed a better understanding of the patterns affecting the occurrence of this type of contaminants. Among them, 2 were never detected (i.e. heroin and amphetamine). Concerning illicit drugs two patterns were found. Cocaine and ecstasy median loads varied considerably between weekdays and weekend days (i.e. 18.3 and 35.9 % respectively) whereas cannabis and heroin (based on 6-mono-acetylmorphine loads) loads were within the same order of magnitude with a significant statistical correlation with pharmaceuticals such as acetaminophen or ketoprofen. 2 The consumption of selected drugs was back-calculated from the loads. Among illicit drugs the highest consumption was found for cannabis with a median consumption of 51 mg.day-1 .inhabitant-1 (inh) whereas the median consumption for cocaine (based on benzoylecgonine loads) and ecstasy was 32 and 6 mg.day-1 .10 3 .inh-1 respectively. The highest consumption values of pharmaceutically active compounds (PACs) were found for acetaminophen and acetylsalicylic acid with 108.8 and 34.1 mg.day-1 .inh-1 respectively, in good agreement with national sales data. A statistically significant weekly pattern was found for several PACs such as metoprolol and trimethoprim, but with the opposite pattern to that of illicit drugs. The variations in daily PAC loads could provide information about the mobility of people in the catchment, especially on the basis of daily taken PACs (i.e. to treat chronicle diseases).