A statistical analysis is applied to find what states of "block" are dangerous from view point of traffic accident. Here, the block is defined to be an area surrounded by some major streets and is feeded by a minor
street network. The accidents under study are those which occur in the whole minor street network. They are grouped into three kinds; pedestrian, vehicle and the gross accidents. And each is classified to three types according to the place where the accident occurs. At the beginning 22 variables are assumed to state a certain relationship of some states of the block with the occurrences of accidents and 12 variables are found significant finally through factor analysis. Further examination has reached several key variables that migth have something significant to cause traffic accidents in the block. The key ones are the number of lanes of street and the number of legs of intersection, especially nearly 2 lanes street and 3-leg intersection, respectively. The case study was carried out on 26 blocks sampled from Osaka City.