We have used nucleic acid hybridization for the detection and grouping of human rhinoviruses (HRV) according to their genetic relationships. Fifteen rhinovirus reference strains, seventy-one clinical isolates and four enteroviruses were propagated in cell cultures, spotted onto membrane filters and hybridized with radioactively labelled cDNA probes covering different parts of the genomes of HRV-1B, HRV-2, HRV-14, HRV-85 and HRV-89. When the rhinovirus and enterovirus reference strains were tested, the 5\' probe of HRV-2 hybridized with thirteen of the fifteen HRV reference strains, with poliovirus type 3 and with ECHO virus 11. The HRV-14 5\' probe reacted with eleven HRV reference strains and with all the enteroviruses studied. Sixty-nine of the 71 clinical isolates were recognised by the HRV-2 5\' probe, whereas the HRV-14 probe from the same part of the genome hybridized with 54 field isolates. One of the two isolates that remained negative with the HRV-2 5\' probe was detected with the HRV-2 probe that derived from the P2 region of the genome, and the other isolate was not detected by any of the probes. Probes from other parts than the 5\' end of the genome were generally more specific, and clusters could be formed based on the reactivity of the HRV strains with these probes.