An outbreak of epidemic keratoconjunctivitis (EKC) occurred in northern Bohemia [Czechoslovakia] in the summer of 1975; 104 patients were treated. Four strains of adenovirus [Ad] type 29 with low or pronounced cross-neutralization against anti-Ad 15 reference serum and 2 Ad type 8 were isolated from 4 patients. Type 8 strains were only obtained from conjunctiva; type 29 also was noted in stools. From 1 patient, type 8 from conjunctiva and type 29 from stool were isolated simultaneously. Of 22 patients with demonstrable antibody rise, a monotypic response in virus-neutralization test [VNT] against type 29 was detected in 13 and a mixed response against types 29 and 8 in 9. An antibody rise was most frequently demonstrated by VNT, the frequence for VNT alone being equal to the frequency of antibody rise as detected by VNT, hemagglutination-inhibition test and complement-fixation test in combination.