Betamethasone propionate, an anti-inflammatory glucocorticosteroid, was detected in cosmetics with no indication on the label of this compound as an ingredient. The product was formulated as a topical spray or shampoo and labeled to contain zinc pyrithione as the active ingredient. A thin-layer chromatographic analysis was carried out on silica gel plates to provide a first indication about the presence of a compound with steroid structure and reactivity; then high-performance liquid chromatography (HPLC) separation allowed the identification of the corticosteroid agent and its quantification. To identify the corticosteroid agent from these commercial samples we collected the fractions suspected to have ketol steroids by prep HPLC and identified the compound as betamethasone propionate by NMR and MS spectrometry. Then we synthesized the standard for the betamethasone 17-propionate and 21-propionate and quantitate the corticosteroids from the sample by HPLC with that standards. By this method we identified the corticosteroid compounds from some commercial cosmetics such as zinc pyrithione sprays. The finding of betamethasone propionate in the products was shown by comparison to an authenticated standard of betamethasone propionate by retention time on reverse-phase HPLC. Two of the tested products contained betamethasone propionate at the levels of 0.005 ${sim}$ 0.02% and the others were free of betamethasone propionate.