Experimental estimations of the effective surface recombination velocity of the high-low junction (S+) and of the base diffusion length are carried out for Al-alloyed n+pp+ bifacial cells aad the results are presented in form of histograms. These results agree with calculated values of Se, when the characteristics of the recrystallized Si layer and heavy doping effects are taken into account. It is concluded that thick Al layers and high alloying temperatures (over SWC) are necessary to obtain low values of S,r. This conclusion agrees with experimental results of other authors. Recomendations to avoid diffusion length degradation are given and the operating limits of the Al alloying technology are discussed.