Migratory properties of normal peripheral blood lymphocyte subsets were studied with a 3-D collagen gel model. Both the T and B subsets entered the gel at the same rate, but once inside the T subsets migrated signifi-cantly faster than the B subsets. In the T subsets, both the T-helper and T-suppressor cells entered the gel at the same rate, but the former migrated significantly faster once inside the gel. The biological significance of their migrations is discussed.