Rhinovirus was transmitted from experimentally infected volunteers (donors) to susceptible recipients and the efficiencies of spread by hand-to-hand contact and large- and small-particle aerosols compared. Transmission of infection was very efficient by the hand route: 11 of 15 hand-contact exposures initiated infection, compared with one of 12 large-particle (P less than 0.005) and none of 10 small-particle (P less than 0.005) exposures. Rhinovirus was present in nine of 18 (50%) nasal swab specimens, 28 of 43 (65%) hand rinses, and seven of 18 (39%) saliva specimens of donors; geometric mean titers of positive specimens were 10(1.5), 10(1.4), and 10(1.2) tissue culture infectious dose 50/ml (TCID 50/ml), respectively. Rhinovirus was present in 20 of 43 (46%) recipient hand rinses, with a geometric mean titer of 10(1.4)TCID50/ml. Virus on donors\' hands was transferred to recipients\' fingers during 20 of 28 (71%) 10-second hand-contact exposures. These findings support the concept that hand contact/self-inoculation may be an important natural route of rhinovirus transmission.