The occurrence of 8 drugs of abuse and metabolites in the influent and effluent of the 3 Wastewater Treatment Plants (WWTP) that treat wastewater from Valencia was studied in 2011, 2012 and 2013. Target drugs except 6-monoacetylmorphine (6-ACMOR) were detected in 100% of the influents. The WWTPs eliminate cocaine (COC), amphetamine (AMP), methamphetamine (MAMP) and 11-nor-9-carboxy-Δ9-tetrahydrocannabinol (THC-COOH). Benzoylecgonine (BECG) was also efficiently eliminated (93-98%), whereas 3,4-methylenedioxymethamphetamine (MDMA) presented removal rates of 32-57% and ketamine (KET) was not eliminated. The most consumed illicit drugs, according to the estimated concentrations of each compound in the studied WWTPs, were cannabis and COC followed by KET, AMP, MAMP, MDMA and heroin. Environmental risk assessment was evaluated by calculating Risk Quotient (RQ). MDMA and KET could pose a medium risk and low risk, respectively, to the aquatic organisms. Although short-term environmental risk is not worrisome, long-term effects cannot be known exactly.