The article presents findings aimed to determine function of distributing optical heterogeneity (clusters) on sizes in doubly distilled water by narrow scattering angles method and their average sizes and concentration studied by transparency fluctuation method. The experiments showed the cluster size spectrum presented in the water within the range of (1.5-6.0) micron, when the average radius was 2.3 micron, the mean-squared radius reached 2.5 micron. Average radius of the optical heterogeneities in the same water determined by the transparency fluctuation method was 2.6 micron with 2,5·10⁶ cm^-3 of average concentration.

Key words: cluster, water, optical narrow angles method, fluctuation method.