Quantitative data on rhizodeposition under ecologically realistic conditions are scarce. Yet they are necessary to understand various aspects of soil organic matter dynamics. To evaluate the use of C-14 pulse-labelling for rhizosphere carbon budget estimations and to develop a standard labelling procedure, the dynamics of C-14 partitioning and factors affecting the representativity of the assimilated C-14 for the average daily assimilation were investigated. Field-grown spring wheat plants were pulse-labelled with C-14 at five different development stages between elongation and dough ripening. Allocation of C-14 in shoot tissue and soil-root respiration was complete by day 19 after labelling. The distribution of net fixed C-14 was not affected by the time of day when labelling was performed. Therefore, net assimilated C-14 was representative for the average daily net assimilation. The proportion of net fixed C-14 recovered in the shoot increased from 61% at elongation to 85% at dough ripening. In the roots this proportion decreased from 15 to 2% and in soil-root respiration from 14 to 7%, while in the soil organic C the percentage did not change with the development stage. C-14 in roots and soil organic C decreased exponentially with depth. We can conclude that C-14 pulse-labelling of wheat plants with an allocation period of about 3 weeks is a satisfactory method to estimate assimilate distribution at different development stages.