We investigated the superoxide anion scavenging effects of 2-amino-1,3- selenazoles and bis-(2-amino-5-selenazoyl) ketones using a highly sensitive quantitative chemiluminescence method. At 166 microM, the 2-amino-1,3-selenazoles and bis-(2-amino-5-selenazoyl) ketones scavenged in the range of 10.0 to 80.0% of O(2)(-). Bis[2-dimethylamino-5-(1,3-selenazolyl)] ketone exhibited the strongest superoxide anion-scavenging activity among the six kinds of 2-amino-1,3-selenazoles and three kinds of bis-(2-amino-5-selenazoyl) ketones. The 50% inhibitory concentration (IC(50)) of bis[2-dimethylamino-5-(1,3-selenazolyl)] ketone was determined to be 37.1 microM. Thus, bis[2-dimethylamino-5-(1,3-selenazolyl)] ketone acted in vitro as effective and potentially useful O(2)(-) scavenger.