Abstract A theoretical treatment for the aggregation of cellular dispersions in a turbulent fluid is proposed based on the work of Saffman & Turner (1956). The use of an expression for the rate of collisions between cells and cell aggregates which is dependent on the size of the colliding cell particles gives theoretical results which markedly reflect many of the features of cellular aggregation as found experimentally by pulse height analysis using a Coulter counter and particle size discriminator. In particular the shape of the distribution curves, the rate of change of single cell population and the attainment of an equilibrium state as well as the occurrence of cell aggregate redistribution during aggregation are shown to be consistent with aggregation in a turbulent field. It is also shown that the nature of the initial cell aggregate distribution has a very significant effect on subsequent aggregation kinetics. The theory has been applied to the aggregation of two Chinese hamster cell lines and gives a satisfactory explanation of the experimental results.