The increasing use of molecular fingerprints in the epidemiology of bacterial nosocomial infections urgently demands a computerised analysis and storage of corresponding patterns, especially with regard to results obtained at different times and in different laboratories. This paper presents a database system in connection with cluster analysis of clonal relations by using genomic DNA fragment patterns of S. aureus (SmaI-digestion, pulsed-field gel electrophoresis) as an example: The database is operated under MS-Access, version 2.0. The cluster analysis is based on an optimising similarity algorithm.