A total of 146 of 506 ostriches (Struthio camelus) introduced into a quarantine in Denmark died within the first 23 days. The majority of deaths were in young birds up to 10 kg body weight. Avian influenza A viruses (AIVs) were isolated from 14 pools of organ tissues representing seven groups each of three or four ostriches, which died over the first 3 weeks. The AIVs were detected in respiratory tissues, kidneys and intestines. All were subtype H5N2. The intravenous pathogenicity index of each isolate for chickens was 0.0 and the four isolates examined each had the amino acid sequence -P-Q-R-E-T-R*G-L-F- at the cleavage site of the haemagglutinin protein, typical of non-pathogenic AIVs. In addition, an avirulent avian paramyxovirus type 1 virus was isolated from one pool of kidney tissues. Bacteriological examination gave no significant results. The most characteristic pathological findings were impaction of the proventriculus and gizzard, enteritis with stasis and multi-focal necrotic hepatitis.