[en] A method is described for the determination of 17α-hydroxyprogesterone from blood samples obtained by heel prick and dried on filter paper. Discs (10 mm diameter) were cut from the filter paper and extracted in the assay tubes with 1 ml of a methanol/diethyl ether/ethyl acetate (50 : 45 : 5, v/v) solvent mixture. Antibody, tritium-labelled tracer and dextran-coated charcoal were added to assay tubes using a multichannel dispenser. The approach used permits one technician to analyze two series, each of 60 duplicate samples, within one working day. Thus the method is applicable for the centralized screening of suspected cases, while emergency samples may be analyzed at the same time within 4 h. Comparisons with a highly specific but more elaborate technique for the determination of blood 17α-hydroxyprogesterone showed a correlation coefficient of 0.99, and the regression equation for the present method (y) against the established method (x) was y = 1.07x + 2.72. The calculated upper reference limit (mean +- S.D.) for 17α-hydroxyprogesterone in healthy infants from two days to eight years of age was 7.5 ng/ml of serum. (Auth.)