Statistics of coherent radiation propagating in a random medium is ana
lyzed in the framework of diagram technique. The distribution function
for radiation intensity is calculated and it is shown. that only for
small values of the argument the distribution function is a simple exp
onential, as predicted by Rayleigh statistics. For larger values of in
tensity the distribution function differs drastically from the simple
exponential, and the asymptotical behavior is a stretched exponential.
The results obtained are confirmed by numerical simulations.