Active cellular locomotion is a feature of such diverse cell types as lymphocytes and cancer cells. The locomotory phenotype of a cell should ultimately reflect the biochemical basis of different migratory strategies. We investigated the locomotory behavior of five epithelial cell lines and one non-epithelial human cell-line as well as human CD4+ T lymphocytes in a three-dimensional collagen type I matrix using time-lapse video microscopy and computer assisted cell-tracking. Migration velocity was up to 70 times lower in tumor cells (0.1-0.3 microm/min) as compared to T lymphocytes (7-7.5 microm/min), whereas the percentage of spontaneously active cells was up to twice as high in tumor cells (80-90%) in comparison to T lymphocytes (54%). Persistence, i.e. the degree of roaming, varied appreciably between the different cell types. In conclusion, velocity and persistence may describe distinct migration strategies in different cell types, i.e. discerning T cell migration from tumor cell invasion.