We report the synthesis of Cd1-xMnxS nanocrystals with x less-than-or-equal-to 5%. Special care is taken to determine the final manganese concentration in the nanoparticles. The variation of the photoluminescence spectrum of Cd1-xMnxS colloidal solutions as a function of manganese concentration is studied. Characteristic luminescence features such as emission maximum wavelength and lifetime are analyzed. We find that it is possible to isolate contributions from particles containing no, one, or more Mn2+ ions. Dopant distribution among the crystallites is random and obeys to a binomial law. The agreement with this simple statistical model allows to use simple photoluminescence experiments to determine Mn2+ mean concentration and dispersion in Cd1-xMnxS nanocrystals.