A high-density genetic map based on restriction fragment length polymorphisms (RFLPs) is being constructed for loblolly pine (Pinus taeda L.). Consequently, a large number of DNA probes from loblolly pine are potentially available for use in other species. We have used some of these DNA probes to detect RFLPs in 12 conifers and an angiosperm. Thirty complementary DNA and two genomic DNA probes from loblolly pine were hybridized to Southern blots containing DNA from five species of Pinus (P. elliottii, P. lambertiana, P. radiata, P. sylvestris, and P. taeda), one species from each of four other genera of Pinaceae (Abies concolor, Larix laricina, Picea abies, and Pseudotsuga menziesii), one species from each of three other families of Coniferales [Sequoia sempervirens (Taxodiaceae), Torreya californica (Taxaceae) and Calocedrus decurrens (Cupressaceae)], and to one angiosperm species (Populus nigra). Results showed that mapped DNA probes from lobolly pine will cross-hybridize to genomic DNA of other species of Pinus and some other genera of the Pinaceae. Only a small proportion of the probes hybridized to genomic DNA from three other families of the Coniferales and the one angiosperm examined. This study demonstrates that mapped DNA probes from loblolly pine can be used to construct RFLP maps for related species, thus enabling the opportunity for comparative genome mapping in conifers.