In this paper, the measurement procedure for estimation of mobile phone antenna performance is presented. This is achieved by considering the Mean Effective Gain (MEG) relative to half-wavelength dipole antenna as the figure of merit. MEG of 13 commercially available mobile phones is measured using the Telia Scattered Field (TSFM) Method in one channel at each of the GSM900 and DCS1800 bands. The measurements of these handsets are carried out in Rayleigh fading environment, characterized by the XPR obtained from the propagation measurements. The statistics of the measured envelope distribution have been fitted to Rayleigh, Rice and Weibull distributions with corresponding goodness of fit analysis. Further, the investigation focuses on the variation of MEG with the surrounding environment of propagation and also with the position of the mobile phone.