The antibiotic consumption in Sweden was evaluated during the period 1975 to 1987. Consumption was measured in terms of defined daily doses (DDDs), that is, the normally prescribed daily adult doses. During the study period the total consumption varied between 49 and 51 million DDD, indicating a considerable over-use of antibiotics in Sweden. In the various groups of antibiotics, considerable fluctuations were seen. The cephalosporin use increased from 477000 DDDs 1975 to 1795000 DDDs in 1987, which can be explained by an increased use of cefaclor for treatment of respiratory tract infections and by the fact that cefuroxime is the dominant injectable antibiotic in Sweden. Markedly increased usage during the study period was also seen for erythromycin and penicillinase resistant penicillins. There were no obvious medical reasons for those increases. Among the folate inhibitors, sulphonamide usage has been almost completely abandoned during the period and the sulphonamides have been replaced by pivmecillinam, trimethoprim and, lately, norfloxacin for the treatment of urinary tract infections. Reduced usage was also seen for sulphonamide/trimethoprim combinations, probably due to an increased awareness of the risk for side effects to these antibiotics. During the entire period the use of tetracyclines, and especially doxycycline, was extensive--almost 10 million DDDs in 1987. The reason for that remains unclear but there are reasons to assume that these antibiotics are prescribed too frequently.