A method to detect the main cystic fibrosis (CF) mutation delta F508 from dried blood spots, whole blood, or saliva using the polymerase chain reaction (PCR) and time-resolved fluorometry (TRF) is described. Samples are treated by boiling in mild alkaline solution, after which two allele-specific PCR reactions are performed. Allele-specific primers and a common biotinylated primer are used in the amplification reactions. To detect the PCR product, an europium-labeled oligonucleotide, complementary to the biotinylated strand of the PCR product, is used in a solution hybridization. Hybridization is done in streptavidin-coated microtitration wells, making the detection easy to perform. After a washing step, the bound label is detected using a time-resolved fluorometer. To analyze function of the assay, 20 dried blood spot samples were tested. PCR amplification of the deletion region combined with gel retardation assay was used as a control method. In the initial testing, 2 samples giving discrepant results in the two assays were found. In addition, 17 samples from known CF patients together with 6 normal control samples were analyzed. Among these patient samples, 10 homozygotes and 6 carriers for mutation delta F508 were found.