Coalescence of drops in fully developed turbulent flow depends on the size of drops and the properties of the flow. By comparing the size of drops with the Kolmogoroff length scale, collision frequencies of drops have been determined. If lambda > lambda(0), then the collision frequency of drops in a gaseous medium is given as omega(c) similar to (epsilon(R)/a(2))(1/3) and for lambda > lambda(0), it is given as omega(c) similar to (epsilon(R)/nu(c))(1/2) in a liquid medium. New expressions for the fluctuation, thinning, and breaking of the intervening film between drops that is formed due to collisions were also suggested. At various Re and Mo numbers, for the calculation of maximum stable sizes of drops, some equations are suggested. In order to evaluate coalescence and break up rates a new dimensionless number, Ke = eta(c)epsilon(R)/g sigma, is introduced. This number is defined as the ratio of the energy of the turbulent flow to surface energy. As a result of the coalescence of drops, evolution of the distribution function with time is determined from the solution of the Focker-Planck equation. Comparisons of the calculated drop sizes with the experimental data reported in literature showed good agreement.