Application of a thermodynamic model (R. Benedictus, A. Bottger, E.J. Mittemeijer, Phys. Rev. B 54 (1996) 9109) shows that in the crystalline Go-crystalline Ti system amorphization can occur both along the Co-Ti interface and along (high angle) grain boundaries in the Co and Ti sublayers. The model also predicts a preferred composition and a certain Limiting thickness for the amorphous product layer at the interface. These predictions are largely in agreement with experimental data obtained for Co-Ti multilayers at temperatures in the range 523-583 K. A parabolic growth behaviour is observed for the amorphous phase, suggesting diffusion controlled growth. The activation energy for the diffusion in the amorphous phase is (160 +/- 8) kJ/mol. Annealing the specimen for a relatively long time or at a relatively high temperature, causes the amorphous phase to crystallize into an intermetallic phase with a CsCl-type structure and an average composition of Co40Ti60 The orientation relationship between the crystalline Co layers and the crystalline Co40Ti60 phase was found to be Co(1 (1) over bar (1) over bar)//Co40Ti60((1) over bar 10) and Co[110]//Co40Ti60[111] or Co[110]//Co40Ti60[001].