The correct folding of tubulins and the generation of functional ␣-tubulin heterodimers require the participation of a series of recently described molecular chaperones and CCT (or TRiC), the cytosolic chaperonin containing TCP-1. p14 (cofactor A) is a highly conserved protein that forms stable complexes with -tubulin which are not apparently indispensable along the in vitro -tubulin folding route. Consequently, the precise role of p14 is still unknown, though findings on Rbl2p (its yeast homologue) suggest p14 might play a role in meiosis and/or perhaps to serve as an excess -tubulin reservoir in the cell. This paper investigates the in vivo possible role of p14 in testis where mitosis, meiosis, and intense microtubular remodeling processes occur. Our results confirm that p14 is more abundantly expressed in testis than in other adult mammalian tissues. Northern blot, Western blot, in situ hybridization, and immunocytochemical analyses have all demonstrated that p14 is progressively upregulated from the onset of meiosis through spermiogenesis, being more abundant in differentiating spermatids. The close correlation observed between the mRNA expression waves for p14 and testis specific tubulin isotypes 3 and ␣3/7, together with the above results, suggest that p14 role in testis would presumably be associated to -tubulin processing rather than meiosis itself. Additional in vitro 3-tubulin synthesis experiments have shown that p14 plays a double role in -tubulin folding, enhancing the dimerization of newly synthesized -tubulin isotypes as well as capturing excess -tubulin monomers. The above evidence suggests that p14 is a chaperone required for the actual -tubulin folding process in vivo and storage of excess -tubulin in situations, such as in testis, where excessive microtubule remodeling could lead to a disruption of the ␣- balance. As seen for other chaperones, p14 could also serve as a route to lead excess -tubulin or replaced isotypes towards degradation. Cell