Biochemical fractionation of the yeast Saccharomyces cerevisiae has revealed a novel DNA primase activity that copurifies with the major DNA polymerase activity. In the presence of RNA precursors and single-stranded DNA (poly(dT), M13), the DNA primase synthesizes discrete length oligoribonucleotides (apparent length, 8-12 nucleotides) as well as longer RNA chains that appear to be multiples of a modal length of 11-12 nucleotides. When DNA precursors are also present, the oligoribonucleotides are utilized by the accompanying DNA polymerase as primers for DNA synthesis. Copurification of these two enzymatic activities suggests their association in a physical complex which may function in the synthesis of Okazaki fragments at chromosomal replication forks.