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Digested sludge samples from domestic wastewater treatment plants located in Northern Italy were tested as far as the presence of viruses (enteric viruses and coliphages), bacteria (faecal coliforms, salmonella) and helminth eggs is concerned. Heavy metals were also analysed. Escherichia coli bacteriophages and faecal coliforms were isolated from all samples, while salmonellae and helminth eggs were isolated only from four and three out of 27 total samples, respectively. The 66% of sludge samples, 46 and 82% of aerobic and anaerobic digested sludges respectively, showed the presence of enteric viruses (enteroviruses and reoviruses). The virus concentrations ranged from 0.6 to 123 MPNCU/g. Results of this study suggest that significant concentrations of pathogens such as enteric viruses can be present in digested sludge, which showed compliance with Italian legislation. As suggested by other authors, there is the need for surveillance and reference indications both in EU (European Union) and Italian regulations concerning the use of sludge in agriculture. [ABSTRACT FROM AUTHOR]