Adult Hoplopleura erratica sucking lice were labelled using a setal clipping technique. Host exchange for lice marked in this manner was monitored through a small population of dye-marked Eastern chipmunks, Tamias striatus, the normal host of this ectoparasite, in a deciduous woodland in central Tennessee, U.S.A. This was accomplished by frequent host live-trapping, anaesthetization and pelage examinations. Louse transfer was most prevalent during the host summer mating period, presumably because of increased chipmunk contacts. At this time, 66·7% of marked adult lice within the host population transferred. Exchanges between opposite sex hosts were more common and adult males donated most lice; no juvenile chipmunks were recorded as louse donors. A greater proportion of male than female lice transferred. Using the exclusive boundary strip method, all exchanging chipmunks had overlapping ranges or shared at least one boundary line.