Rhinovirus infections may spread by aerosol, direct contact, or indirect contact involving environmental objects. We examined aerosol and indirect contact in transmission of rhinovirus type 16 colds between laboratory-infected men (donors) and susceptible men (recipients) who played cards together for 12 hr. In three experiments the infection rate of restrained recipients (10 [56%] of 18), who could not touch their faces and could only have been infected by aerosols, and that of unrestrained recipients (12[67%] of 18), who could have been infected by aerosol, by direct contact, or by indirect fomite contact, was not significantly different (chi 2 = 0.468, P = .494). In a fourth experiment, transmission via fomites heavily used for 12 hr by eight donors was the only possible route of spread, and no transmissions occurred among 12 recipients (P less than .001 by two-tailed Fisher's exact test). These results suggest that contrary to current opinion, rhinovirus transmission, at least in adults, occurs chiefly by the aerosol route.