An outbreak of methicillin-resistant Staphylococcus aureus (MRSA) occurred in a neonatal intensive care unit (NICU) over a period of 2 months involving 16 babies, mainly of low birth weight. Arbitrary grouping of the isolates showed that there were apparently three different strains involved in the outbreak, as determined only by antibiogram. Twenty-three out of 27 isolates were allocated to 'group 1' based on antibiotic sensitivity pattern. Control of spread of the MRSA in the unit was difficult because of some technical constraints but eradication was finally achieved by cohort nursing and treatment with topical mupirocin in paraffin base. All MRSA isolates were resistant to gentamicin, erythromycin, tetracycline and at least four other antibiotics but sensitive to vancomycin. Overcrowding, limited space, inadequate cleaning of the equipment and initial lack of correct attitude to scrupulous handwashing techniques, all appeared to contribute to the ease of spread of the strains involved.