The appearance of counterfeit medicines in supply chains is a global public health problem that may seriously affect patients. Counterfeit drugs do not meet quality standards and do not declare their real composition and/or source for the purposes of fraud. They may be generic or innovative, they may contain genuine constituents in a fake packaging, or wrong ingredients, or inactive ingredients, or an incorrect quantity of the active substance. In Croatia, no cases of counterfeit medicines have been detected so far, but the Agency for Medicinal Products and Medical Devices has received 34 samples of medicines and other products for testing from Zagreb City Police. The samples included medicines for erectile dysfunction: sildenafil, tadalafil, and vardenafil. Twenty-three samples of tablets without marketing authorisation in Croatia were tested with high-performance liquid chromatography (HPLC) for the declared sildenafil and tadalafil content. Samples labelled 1 (batch T/33), 3 (batch T/33), 5 (batch 4), 6 (batch M0016J), 10 (batch T-070235), 12 (batch T-070544), 15 (batch 314833201), 16 (batch 832718474), and 17 (batch 504830028) containing sildenafil and samples labelled 20 (batch 070356), 21 (batch 05668), and 22 (batch T 378 5) containing tadalafil did not contain the active substance within the acceptable 95 % to 105 % margin of deviation from the declared content. While most samples cannot be described as fake with a reasonable amount of certainty, there is still a suspicion of counterfeit. A correct conclusion can be drawn only with the assistance of the manufacturers and by conducting additional laboratory tests.