All cases of neonatal septicaemia during 1981-94 were studied at Orebro Medical Centre Hospital, Sweden. One hundred and thirty-two children fulfilled laboratory and clinical criteria for neonatal septicaemia and were included. Staphylococcus aureus (n = 41), Group B streptococcus (GBS) (n = 32) and coagulase-negative staphylococci (CoNS) (n = 27) were the dominating aetiologies. The annual incidence of septicaemia increased significantly, from 2.3 cases during the first 7-year period to 3.3 per 1000 live births during 1988-94. This increase was caused by S. aureus and CoNS, which mainly affected premature children and had an onset more than 48 h after delivery. GBS, on the other hand, slightly decreased and affected full-term children within 48 h. The overall mortality was 11%. CoNS isolated during the latter 7-year period were more resistant to antibiotics than those isolated during 1981-87; resistance to methicillin increased from 14 to 45% and to gentamicin from 0 to 20%. These changes in aetiology and antibiotic susceptibility should be considered when selecting antibiotic treatment in neonatal septicaemia.