Septoria nodorum, detected in wheat seed by isolating on ox gall agar, increased 1–25% during storage up to 24 months after harvest. S. nodorum detection increased more rapidly in seed lots stored at 25 °C than at 5°. This increase was generally related to a decrease in other seed fungi, especially Alternaria and Epicoccum. These fungi were competitive with but not antagonistic to S. nodorum on ox gall agar. The ox gall agar assay was preferred because of its accuracy and savings of time and labour. The differences of these results from those of some other workers were not related to assay procedures or the initial percentage colonization of the seeds by S. nodorum.