Hydroxylation of adamantane using whole cells of bacteria, actinomyces, and molds was examined. The structure of the product was determined using gas chromatography (GC), nuclear magnetic resonance (NMR), and mass spectroscopy (MS). Among 470 strains tested, Streptomyces griseoplanus was highly regioselective to give 1-adamantanol (0.096 mmol) from adamantane (0.3 mmol) in a 32% molar conversion yield after 72-h cultivation in the presence of 3% (v/v) Tween 60. A P450 inhibitor such as 0.5 mM 1-aminobenzotriazole or menadione significantly inhibited the hydroxylation activity. These results suggested that a P450 oxidation system might be involved in this hydroxylation reaction.