GeMS, the Gemini MCAO system, is undergoing commissioning. Using 5 laser guide stars and a central launch, GeMS is particularly sensitive to Rayleigh backscatter and the fratricide effect. Using data covering a 5 months period from January to May 2011, we present results on (i) the Sodium return and its variability from night to night, (ii) the spot elongation and (iii) the fratricide effect. A simple modeling of the fratricide is presented as well as possible strategies for mitigation.