[en] The non-radioactive biotin labelling method was employed to label bacteriophage lambda DNA. During hybridization, 1% casein was used instead of the commercial blocking reagent. DNA hybrids were detected by chemiluminescent technique. Some washing steps were detected or shortened to expedite the procedure. Steps which can be lengthened and can serve as stopping points during washing were identified. The introduced modifications did not alter the sensitivity of this nonradioactive nucleic acid detection method. Comparison of this method with the radioactive labelling and detection showed no difference in sensitivity. (Author). 4 refs.; 2 figs