By using sticky and shelter traps population densities of the American cockroach, Periplaneta americana (L.), in low.income apartments in Pusan were studied from July, 1984 to March, 1986. During the investigation period the peak densities mostly appear며 between Agust and October. In some apartments, however, cockraoches were collected in a great number in winter. In the apartment building the highest number of American cockroaches was consistently observed at 2~3 focus apartments in all seasons. The focus apartment changed to another apartment in spring or autumn. Within the apartment more than 50% of American cockroaches were collected in the kitchen on the average. The next abundant habitat was the room, followed by the loft. In spring or autumn, however, the highest number of cockroaches was collected in the floor. In unclean environments of low-income apartments the cleanness within the apartment appeared not to be correlated with the densities of the American cockroach collected by sticky traps.