This retrospective study investigated the records from July 1985 to June 1986 of all medical visits due to acute respiratory tract infections (RTIs) in infants aged 1-3 years. The study, in a municipal district, included all visits to the district health centre as well as visits to the paediatric and ear, nose and throat departments of the nearby hospital. The study population consisted on 489 children, of whom 140 were cared for in day-care centres (DCC), 146 in family day-care (FDC), while 203 did not receive any sort of municipally-supported day care (home care, HC). During the year studied, 223 children needed treatment by a doctor for acute RTI on altogether 499 occasions leading to the prescription of 325 courses of antibiotics. As regards RTIs as a whole and regarding those treated with antibiotics, the incidence density was greatest among the DCC children and lowest among the HC children, while the FDC children formed an intermediate group.