A 1-year stability study of ampouled polycyclic aromatic hydrocarbon (PAH) solutions was carried out. Two solutions of seven pure PAHs were prepared, one in acetonitrile and one in toluene, and ampouled. Solutions were tested for mass concentration and impurities before and after ampouling. No differences were found. After 0, 3, 6, 9 and 12 months, three ampoules were selected for analysis from the acetonitrile and the toluene lots stored at +20 degrees and at -20 degrees C. The acetonitrile solution was analysed by high performance liquid chromatography and the toluene solution by glass capillary gas chromatography. The results demonstrate that both solutions were stable and no contamination occurred during storage.