Omeprazole has been associated with multiple adverse effects including skin reactions but, to date, cutaneous hyperpigmentation has not been described as an adverse effect of this drug.We describe a case of a 52-year-old Caucasian woman who developed skin hyperpigmentation in the upper trunk, mimicking ashy dermatosis, 2 months after initiating omeprazole treatment. Histopathologic examination of a skin biopsy taken from a pigmented macule showed dermal macrophages containing golden-brown granules, which also displayed a sulphur peak on energy-dispersive X-ray microanalysis. High-performance liquid chromatography (HPLC) and mass spectrometry were also performed on the drug and on a biopsy specimen revealing the same chromatograms as well as the same mass spectra.According to our results, omeprazole itself may induce cutaneous pigmentation and, to our knowledge, this is the first report of this finding.