Asynchronous infections of MA104 cells with temperature-sensitive (ts) mutants of simian rotavirus SA11 were performed to determine if the superinfecting ts mutant could contribute to the formation of reassortant progeny. Significant yields of ts+ reassortant progeny were obtained in crosses where infection with the first and second ts mutant was separated by as much as 24 hr, indicating that superinfecting viruses were not excluded from participation in genetic interactions. The practical and theoretical implications of this result are discussed.