To determine how many family members of methicillin resistant Staphylococcus aureus (MRSA) patients were colonised with MRSA and how this colonisation developed over time.Descriptive, prospective.Two laboratories notified the Public Health Services of newly-diagnosed MRSA patients in three provinces of the Netherlands. These persons and their family members were screened for MRSA colonisation at baseline, after 3 to 4 months and after 6 to 12 months. No advice on medical intervention was given. Relevant medical interventions by general practitioners were registered.Nineteen index patients and their families were included. A total of 41% of the family members (n = 44) proved MRSA positive on at least one of the three tests. At second follow-up the proportion of colonised family members had decreased slightly from 32% to 27%; by the end of the study only a third of the index patients were still MRSA positive. Colonisation of index patients was more persistent if family members were colonised as well.A large and changing number of family contacts of MRSA-positive patients were shown to be colonised over time, and sometimes in the longer term.