In Japan, activities to prevent crime by citizens have been encouraged, but are not developing well. Two studies were carried out to examine factors regulating citizen participation in activities to prevent crime in Edogawa ward. In a survey interview of 15 leaders of activity to prevent crime (Study 1), it was suggested that attachment to city, attitude towards activities to prevent crime, indirect support from administration, and mutually beneficial relations with administration led to development of these activities. In a survey of 141 randomly sampled adults (Study 2), people who participated in activities to prevent crime accounted for 14.2% of the total. Among men, participation was determined by the number of organizational affiliations in the community. Intention to participate was promoted by advanced age and high levels of political interest. In women, participation was determined by youth, number of schoolchildren in the family, and communication with neighbors. Intention to participate was restrained by low levels of political interest and absence of high-school children in the family. Implications for activities to prevent crime were discussed from the viewpoint of gender and benefit from activity.