Aims: To evaluate the consequences of criminalising khat, with a focus on the changes in law enforcement and the use, availability, price and quality of khat in the Netherlands. Methods: Mixed methods, including law enforcement data, expert interviews, focus group interviews with members of the Somali community, and a survey among 168 current (last month) khat users. Findings: Soon after the law changed (early in 2013), and khat had become an illicit drug, much of the khat imported from Africa was confiscated at Schiphol International Airport and users found it more difficult to obtain fresh khat leaves. About two years after the ban had been implemented, the price of fresh khat at user level had increased tenfold on average, and much of it was of poorer quality (e.g. sold in dried or powdered form). Conclusion: Criminalisation of khat in the Netherlands had substantial consequences for the khat market, predominantly because the ban was actively enforced at a crucial stage in the distribution chain (transcontinental import by air) and there was a lack of alternative transportation routes that could supply users with fresh khat. It is highly likely that the total number of Somali khat users in the Netherlands dropped, but that the proportion of dependent and poor, ''problem users'' increased.