- A perturbation method is presented which can be applied to the description of a wide range of physical problems that deal with dynamics of dipolarly coupled spins in solids. The method is based on expansion of eA+B in a perturbation series. As an example of the application of the method, the multiple-quantum coherence dynamics in three- and four-spin clusters are considered. The calculated 0Q and 2Q intensities versus the duration of the preparation period give close agreement with exact results and simulations data. The exact solutions for J0Q and J2Q coherences in four-spin systems are obtained.