The growth of wheat plants and the distribution of labelled photosynthate from pulse-labelling with 14CO2 were measured periodically during the growing season in the field. During early growth there was approximately the same proportion of photosynthate translocated below ground and retained in the shoots. Of the 14C below ground about a half was respired and a quarter each was in the soil and roots. This distribution changed exponentially during growth with an increasing proportion of 14C remaining in the shoots and a corresponding decreasing proportion being translated below ground, which was only a few percent by flowering. From this information the total input of carbon to the soil from the crop was calculated to be 1305 kg Cha−1. Comparison of these estimates with those from previous experiments suggest that differences do occur due to the stage of growth of the plant, the environmental conditions, soil type and microbial activity.