Characteristics the organisation of infection control in hospitals participating in the Active Nosocomial Infections Surveillance System in Poland. Analysis of the data obtained from a questionnaire on organization of nosocomial infections surveillance in hospitals participating in the Active Nosocomial Infections Surveillance System coordinated by the Polish Society of Hospital Infections. Analyzed data were obtained from 32 hospitals of different size number of hospital beds) and type of reference. Most questions focused on the structures of infection control, postdischarge surveillance and role of microbiological laboratory. NIs surveillance system is based on the work of infection control team consisting of epidemiological nurse and physician representing different specializations, but there is no specialist or doctor specializing in medical microbiology. Additionally, the Infection Control Committee exists in 25 hospitals. Only in 37.5% of those hospitals the postdischarge surveillance is performed, but related only to surgical site infections. There is no microbiological surveillance in 25% of the hospitals, which means that neither registration nor collecting of drug-resistant strains are performed. Implementation of the Active Nis Surveillance System is based on the common organizational structure, programme and definitions of infections. The postdischarge surveillance and microbiological surveillance are the main activities which still need improvement.