The distribution of microorganisms in 15 samples of selected spices and the effects of irradiation of them were studied. The total aerobic bacteria in black pepper, white pepper, turmeric, rosemary and basil were determined to be 3 × 103 to 5 × 107 per gram. Coliforms were also determined in 8 samples to be 2 × 102 to 2 × 106 per gram. The main aerobic-spore-formers were identified as Bacillus pumilus and B. subtilis. Molds were determined in 10 samples to be 1 × 102 to 2 × 104 per gram which consisted mainly of the Aspergillus glaucus, A. restrictus, A. flavus, A. fumigatus, A. niger groups and Penicillium. A study on the inactivation of microorganisms in spices showed that gamma-irradiation doses of 1.2 to 1.5 Mrad were required to reduce the total aerobic bacteria to below a detectable level, while doses of below 1.0 Mrad were required to decrease the spore-forming bacteria to below 103 per gram, the Japanese hygenic standard. Goliforms were eliminated with 0.4 to 1.0 Mrad irradiation. In the storage s...