Organ cultures of human embryonic trachea in test tubes were used as an adjunct to tissue cultures in the isolation of respiratory viruses from children in hospital. Fifty-one viruses were obtained from 127 specimens, giving an isolation rate of 40%. Fifteen viruses were isolated from the original tissue cultures and also after passage through organ culture. Thirty viruses were isolated from the original tissue culture only, and six viruses only from organ culture (three para-influenza, one influenza A, and one rhinovirus). An increase of 5% in virus isolation rate over that of standard tissue culture was obtained.