Abstract: The present invention is directed to a method for detecting the presence or absence of any specific target nucleic acid sequence contained in a sample. The target sequence can be present in the sample in a relatively pure form or as a component of a member of a mixture of different nucleic acids. The method of the invention utilizes a novel primer design. The sequence of the novel primer is composed of two portions, the 3' portion is a primer specific for the desired nucleic acid sequence and the 5' portion is complementary to preselected nucleic acid sequence. Extension of the 3' portion of the primer with a labeled deoxynucleosides triphosphate yields a labeled extension product if, but only if, the template includes the target sequence. The labeled extension product is detected by hybridization of the 5' portion to the preselected sequence. The preselected sequence is preferably bound to a solid support as one member of a grid having a group of sequences.