This study presents data on the intra-herd prevalence and colonisation dynamics of Methicillin-resistant (MRSA) and Methicillin-sensible (MSSA) Staphylococcus aureus in two independent pig herds located in the Northwest of Germany. Swabs taken from the nasal cavity of sows and piglets, from the udder of the sows and from the direct environment of the pigs were tested microbiologically for MRSA and MSSA. The piglets were identified individually, tested at birth and then swabbed again every 3 weeks from birth to sale at the end of nursery with 25 kg (farm A), and at slaughter respectively (farm B). The intra-herd prevalence differed between the two farms remarkably. In addition, both farms differed concerning the point in time of the first detection of MRSA in piglets: While MRSA was detected in piglets on farm A within three days after farrowing, positive results in piglets did not occur before three weeks of life on farm B. An MRSA-positive result of the sow increased the number of MRSA-positive piglets on days 1-3. Moreover the results of this study support the suggestion, that an early colonisation of the piglets with Methicillin-sensitive S. aureus (MSSA) has a protective effect. Over time, the pigs changed their pigs revealed that the proper cleaning and disinfection on one of the study farms had a reducing effect on the MRSA occurrence in the farrowing pens and in the flat deck.