A porcine group C rotavirus (strain Cowden-AmC-1) was adapted and serially passaged in an established diploid swine testicular cell line (ST cells). Growth of group C rotavirus in ST cells, which in maintenance medium required trypsin, but not pancreatin resulted in cytopathic effect characterized by cellular stranding and subsequent cell lysis. Active replication and assembly were confirmed by RNA profile analysis, immune electron microscopy and immunofluorescence. Adaptation of non-group A rotavirus to a continuous cell line has not previously been reported and should facilitate progress in diagnostic procedures and vaccine development.