The study developed qualitative and quantitative indicators to evaluate group work effectiveness with MSM (efficiency, effectiveness, economy) in terms of prevention of HIV infection, as well as the algorithm to calculate the cost of group events based on NGO budgets. Analysis and evaluation of direct and indirect results, effectiveness of group forms of work, and their effect on the prevention of HIV infection among MSM was conducted by comparing the relative indicators calculated for the main group (it included MSM who received both group and personal HIV prevention services) and the control group (clients who received preventive services only individually).