We discuss two twist-3 spin asymmetries in $pp$ collisions. One is the transverse polarization of hyperons produced in unpolarized $pp$ collisions, and the other is the spin asymmetry for the hadron production in the collision between the longitudinally and transversely polarized protons. The former is a naively ``$T$-odd" observable, while the latter is a naively ``$T$-even" one, and this leads to inherently different form of the corresponding twist-3 cross sections. Since both asymmetries occur as a result of multi-parton correlations
either in the initial protons or in the fragmentation process, they play a complementary role to test the theoretical framework and to give an insight on the hadron structure. Measurement of these asymmetries at RHIC will be particularly interesting.