Recent discussions of relationships within seed plants have focussed on the correct placement of the Gnetales. Some phylogenetic conclusions based on DNA sequence data have placed this group as sister to conifers or even within the conifers. Contrary to this, phylogenetic analysis of sequence data from the chloroplast gene rps4 places Gnetales as sister to all other living seed plants. Bootstrap support for this result is increased by adding rbcL and 18S rDNA sequence data to the analysis. Angiosperms comprise a branch located between Gnetales and other living seed plants. The paraphyly of living anthophytes (Gnetales and angiosperms) contradicts the anthophyte theory, but also modifies significantly the interpretation of character evolution deduced from trees presenting Gnetales as coniferophytes. Within conifers, there is robust support for Pinaceae as sister to other conifers, followed by an Araucariaceae/ Podocarpaceae clade. The crown group includes Cupressaceae s.l., Cephalotaxus, Sciadopitys, Taxaceae, and Torreyaceae. This group of “yew-conifers” is also found in trees based on rbcL and 18S rDNA. The rps4 gene proves useful at the level of seed plant family relationships, but also includes more variable regions that have utility between genera.

Key words: conifer, Gnetales, phylogeny, rps4, seed plant