Online shopping is on the rise and this extends to purchasing of medicines. Patients can deliberately or unwittingly purchase medicines from one of the many illegal suppliers. On this illegal market, erectile dysfunction medicines play a prominent role. We estimate that at least 70% of sildenafil used in the Netherlands is purchased from illegal suppliers. Price cuts on the legal market with the introduction of generics have not made a difference. It is important to gain an insight into the scale of illegal use of medicines and the potential harmful effects we may encounter.