The attack density and brood production ofTomicus piniperda(L.) (Col., Scolytidae) were recorded on stems ofPinus sylvestrisL. felled in southern, central, and northern Sweden before, during, and after the spring flight period in 1977 and 1978. The study sites were adjacent to stands clear‐felled during the last or the previous winter. The attack density (i.e., the number of egg galleries per m2inner bark area) varied considerably between localities and years. At all sites high attack densities were recorded in trees felled before or soon after the flight commencement, whereas few attacks occurred in trees felled in late May or later. The availability of brood material did not affect the seasonal attack pattern in any consistent way. The brood production varied from zero to more than 900 individuals per m2.