Here we present a novel hypothesis for the origin of overlapping open reading frames (O-ORFs) observed in the 'non-coding frames' of several genes of yeast chromosome II. By computer analysis it was found that the specific amino acid content and base distribution pattern at certain genomic locations and the presence of O-ORFs were related. This observation prompt us to conclude that these O-ORFs are mere statistical curiosities without any biological function, which is in contrast to the hypotheses proposed by other authors.