The comparison of two-dimensional protein patterns from wheat alloplasmic lines (etiolated seedling stage) has allowed us to define three variable polypeptides with a cytoplasmic determination: the large subunit of ribulose bisphosphate carboxylase/oxygenase and two other polypeptides that are likely to be two forms of the chloroplastic beta subunit of ATP synthase. Two cytoplasmic types are found among the Triticum species. Of the diploids studied only T. speltoides and T. aucheri had these same cytoplasmic markers as T. aestivum. T. turgidum and T. timopheevi.