Probenecid is a well-established drug for the treatment of gout and is thought to act on an organic anion transporter, thereby affecting uric acid excretion in the kidney by blocking urate reuptake. Probenecid has also been shown to affect ATP release, leading to the suggestion that ATP release involves an organic anion transporter. Other pharmacological evidence and the observation of dye uptake, however, suggest that the non-vesicular release of ATP is mediated by large membrane channels with pannexin 1 being a prominent candidate. Here we show that probenecid inhibits currents mediated by pannexin 1 channels in the same concentration range as observed for inhibition of transport processes. Probenecid did not affect channels formed by connexins. Thus, probenecid allows for discrimination between channels formed by connexins and pannexins.