A total number of 1105 cases with viral conjunctivitis, mainly epidemic kerato-conjunctivitis (EKC) consisting of 354 cases from Sapporo, Japan, of 628 from Kaohsiung, Taiwan and of 123 from Busan, Korea, encountered during the periods, 1980-81 and/or 1983, were studied aetiologically and epidemiologically. Patients were aged from 27 days to 88 years with a peak in the 20-29 year age group. Aetiological diagnoses were established in 610 cases (55%), consisting of 536 cases (49%) caused by adenoviruses and of 74 (7%) by EV 70. The most frequently detected agent was Ad 8 (57%), followed by EV 70 (12%), Ad 3 (9%) and Ad 19 (7%). The aetiological profiles of viral conjunctivitis were generally similar in three cities of East Asia. EKC (70%) was mainly caused by Ad 8, Ad 19 and Ad 37, but AHC (13%) by EV 70 and PCF (5%) by Ad 3 and Ad 11. Ad 19 and Ad 37 isolates in three cities were compared with the cleavage patterns with restriction endonucleases, BamHl, Smal, Sall and Hindlll. All of the Ad 19 isolates tested were identical to Ad 19a reported by Wadell et al, and all but three isolates of Ad 37 were identical to the Ad 37 prototype prevalent in Europe and the US. The three isolates of Ad 37, different from the prototype in cleavage pattern with Hindlll, designated as Ad 37A, were detected in Sapporo and Kaohsiung in 1980. From the cleavage patterns with four restriction endonucleases, Hindlll, BamHl, Sa1l and Sstl, the Ad 8 isolates in 1983 were divided into three subtypes, which were associated with the cities isolated.(ABSTRACT TRUNCATED AT 250 WORDS)