This study was undertaken to determine the distribution of phage types of Staphylococcus aureus isolates from hospital outbreaks or sporadic cases received in our laboratory during the past 14 years. The records for 15,803 isolates from 55 Spanish hospitals have been analysed. In relation to sporadic isolates we have been able to detect the predominance of phage group I and non-typable staphylococcal strains. Since 1989, we have observed a considerable increase in hospital infection caused by methicillin-resistant S. aureus strains which we could differentiate in to two groups; one belonging to phage group III (6/47/54/75/77/84/85) and other groups of nontypable strains which could be classified as phage group I-III after heat treatment (29/77/84) and with similar patterns by reverse typing (6/47/53/54/75/83A/84/85/W57/1030/18042). During 1990 and 1991, these strains have extended widely to at least six different autonomous regions creating an epidemic situation in Spain.