  Predictions for the single transverse spin asymmetry A_N in semi-inclusive
DIS processes are given; non negligible values of A_N may arise from spin
effects in the fragmentation of a polarized quark into a final hadron with a
transverse momentum k_T with respect to the jet axis, the so-called Collins
effect. The elementary single spin asymmetry of the fragmenting quark has been
fixed in a previous paper, by fitting data on p(transv. polarized) + P -> pion
+ X, and the predictions given here are uniquely based on the assumption that
the Collins effect is the only cause of the observed single spin asymmetries in
p(transv. polarized) + p -> pion + X. Eventual spin and k_T dependences in
quark distribution functions, the so-called Sivers effect, are also discussed.
