A national wastewater-based epidemiology (WBE) monitoring campaign has been initiated to determine the trends in drug consumption in Turkey since 2019. This study aimed to present the wastewater monitoring results for four periods in 2019 for six major cities with 17 wastewater treatment plants. The study investigated heroin (HER), amphetamine (AMP), methamphetamine (METH), cocaine (COC), 3,4-methylenedioxymethamphetamine (MDMA), cannabis, alcohol, and tobacco to understand the temporal and geographical drug consumption trends. The results indicated a trend of regular cannabis use in all the cities. Considering geographical variations, the drug usage trends were not homogeneous within the country for any of the investigated drugs, except cannabis. HER consumption was predominant in Denizli (1042.48 mg/1000 inh/day), while Izmir and Antalya (154.10 and 79.56 mg/1000 inh/day, respectively) topped for COC consumption. Aydin had the highest consumption levels of AMP (90.03 mg/1000 inh/ day) and METH (358.13 mg/1000 inh/day), while MDMA consumption was the highest in Samsun (157.64 mg/1000 inh/day). Tobacco consumption was high in Aydin (8791.69 mg/1000 inh/day) and Antalya (5375.17 mg/1000 inh/ day), whereas alcohol consumption was higher in Bursa than in the other cities (53434.61 mL/1000 inh/day). There were no statistically significant differences in the weekend consumption levels of the investigated drugs among these six cities. Although this study included the results of 1 year of consumption monitoring, the data confirms internationally published information on the drug trafficking routes of conventional drugs in this region, especially the Heroin-Balkan route. Results from further sampling will enable accurate evaluation of global drug consumption and trafficking, in addition to alcohol and tobacco use. (c) 2021 Elsevier B.V. All rights reserved.