Dynamical behavior of atmospheric molecular clusters was investigated. A model was developed to describe the evolution, concentration and sources of atmospheric clusters. The model includes sources of monomers, monomer — i-mer collisions and evaporation of i-mers. The developed model is agile and flexible. The evaporation rate is shown to be most important parameter describing the growth of clusters. The existence of dimers, trimers and bigger i-mers depends mainly on evaporation rate. In practice, the evaporation rate should be smaller than 1s −1 for atmospheric nucleation to occur.