Paclitaxel is mainly eliminated by CYP2C8 in the liver. CYP2C8 is strongly inhibited by the clopidogrel metabolite acyl-β-D-glucuronide. To determine if this interaction has clinical relevance, we identified 48 patients treated with clopidogrel and paclitaxel using databases and a prescription register. Peripheral sensory neuropathy was retrospectively evaluated from medical charts and compared to that of 88 age- and sex-matched controls treated with paclitaxel and low-dose aspirin. By a cumulative dose of 1,500 mg paclitaxel, 35% of the patients had developed severe neuropathy. The overall hazard ratio between clopidogrel use and severe paclitaxel neuropathy was 1.7 (95% confidence interval, 0.9–3.0). Among those receiving a high-dose paclitaxel regimen, the hazard ratio was 2.3 (95% confidence interval, 1.1–4.5). Our study indicates that clopidogrel is associated with a clinically relevant increased risk of neuropathy in patients treated with high-dose paclitaxel.