Virological and serological data from 242 patients with conjunctivitis or keratoconjunctivitis, infected with adenovirus type 8, and of 109 patients infected with other adenovirus types were compared by means of an electronic data processing system. About 55% of the patients in both groups showed a diagnostic antibody rise in genus-specific (antihexon) complement-fixation. This rate is significantly lower than that obtained with genus-specific ELISA IgG or IgA, or with neutralization tests against the homologous virus, or with hemagglutination-inhibition in case of adenovirus 8 infection. All these tests showed titer rises in 72 to 85% of the patients; differences were not significant. Virus isolation from conjunctival swabs, taken up to 9 days after onset of disease, was successful in 80 to 90%, thereafter in 30%. The time-course of the various antibody titers showed that genus-specific (antihexon) antibodies mostly rise 9 to 12 days after onset, whereas type-specific neutralizing or hemagglutination-inhibiting antibodies rise 10 to 14 days after onset.