Food-borne diseases nosocomial outbreaks due to Salmonella enterica strains have a high incidence nowadays. We describe here an outbreak that occurred in July 1990 in the Malaga University Hospital, that only involves one shift of health care workers. Salmonella enterica was detected in stool samples from HCW and a first analysis revealed the presence of two different antibiotic susceptibility patterns (resistotypes) among isolated strains. Two months after the outbreak started, the CNVIS (Majadahonda, Spain) confirmed the presence of two different serotypes (bovismorbificans and enteritidis). The delayed availability of the results (due to the lack of specific sera needed in most of the clinical Laboratories) was responsible for finishing only a partial and restricted epidemiologic study in terms of source identification for one particular serotype as well as for the antimicrobial resistance studies. The molecular identification techniques, particularly the electrophoretic protein profile could overcome these problems.