An outbreak of epidemic keratoconjunctivitis (EKC) occurred in northern Bohemia in the summer of 1975. One hundred and four patients were treated. Four strains of adenovirus type 29 with low or strong pronounced cross-neutralization against anti-Ad 15 reference serum, and 2 adenovirus type 8 were isolated of 4 patients. Type 8 strains were only obtained from conjunctiva, type 29 also from stools. From one patient, type 8 from conjunctiva and type 29 from stool were isolated simultaneously. Out of 22 patients with demonstrable antibody rise, a monotypic response in virus-neutralization test against type 29 was detected in 13 and a mixed response against types 29 and 8 in nine. An antibody rise was most frequently demonstrated by virus-neutralization test, 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.