  We show that there is an effect of nonextensivity acting upon the BCS model
for superconductors in the ground state that motivates its study in the
Tsallis' statistical framework. We show that the weak-coupling limit
superconductors are well described by $q \sim 1$, where q is a real parameter
which characterizes the degree of nonextensivity of the Tsallis' entropy.
Nevertheless, small deviations with respect to q = 1 provide better agreement
when compared with experimental results. To illustrate this point, making use
of an approximated Fermi function, we show that measurements of the specific
heat, ultrasonic attenuation and tunneling experiments for tin (Sn) are better
described with q = 0.99.
