Different methods for labelling polymerase chain reaction (PCR) products with non-radioactive labels for their detection by hybridization with immobilized DNA probes were compared. The use of digoxigenin ( DIG) as a label provided greater sensitivity than biotin in a PCR system targeting the invA gene from Salmonella typhimurium. Incorporation of digoxigenin into amplicons in the form of 5'-DIG-labelled oligonucleotide primers resulted in better assay signals and was more economical than DIG-labelled dUTP.