Nuclear growth, microspore cell growth and cell cycle stage were examined in microspores of anthers of Hordeum vulgare L. cv. Klages taken from florets of the middle of the spike as per anther staging methods. Although there was wide variation in nuclear size at all stages of the cell cycle, mean nuclear size appeared to be a good indicator of cell cycle stage for microspores within anthers. Microspore cell size increased considerably during Gl of the cell cycle. Anthers bearing microspores cytologically characterized as in the mid-uninucleate stage, which have proven to yield high levels of callus production, were determined to be in G1 of the cell cycle and were regularly found in spikes taken from tillers in which the base of the flag leaf had emerged 0 to 3 cm above the penultimate leaf.