Investigate the epidemics for influenza outbreaks. The outbreak pattern of the internal patients housed in the 10 designated hospitals was monitered to investigate and the characteristics of the virus isolates are as follows. 232 strains of influenza virus was isolated from the oral specimen of 1,320 respiratory disease patients in Pusan from Oct. 1998 to Jun. 1999. Among these isolates, 222 strains were A-type and the rest were B-type. The outbreak pattern for sex-and age-groups is as follows. The male outbreak was similar to the female outbreak: male outbreak, 47.4% and female outbreak, 52.5%. Most of the patients were less than 10 years old. The monthly influenza outbreak was consistent from Dec. 1998 to Apr. 1999. and The 113 strains from the A-type isolates were A/ Sydney/05/97(H3N2)-like, the 109 strains were A/Beijing/262/95(H1N1)-like, and all of the 10 B-type isolates were B/Harbin/07/94-like.