Clinical and epidemiological observations on 87 cases of donovanosis seen at Port Moresby General Hospital are presented, with detailed reports of three cases in which the disease was more severe. The circumstances of infection described were consistent with venereal transmission. Chloramphenicol and gentamicin were effective in curing the disease, while streptomycin was found to be ineffective in a number of cases tested. Complement-fixation tests with Donovania antigen revealed the presence of antibodies in all but one of 23 cases tested, and in nine out of fourteen other patients who on clinical grounds were suspected of having donovanosis but were negative by smear test. The complement-fixation test with Klebsiella antigen was found to be highly specific for donovanosis, but less sensitive than the test using Donovania antigen. The intracellular location of Donovania in tissue and the presence of antibodies which are apparently not protective suggest that cell-mediated immunity may be important in defence against Donovania infection.