We investigate the application of the techniques of coherent control to ultracold atom collisions. Laser-cooled Rb atoms in a magneto-optical trap are induced to collide by pulses of frequency-chirped light. The influence of various chirp parameters on these collisions is studied: chirp-rate, laser intensity, center detuning of the chirp, and delay between two successive chirps. These experiments reveal two coherent processes: rapid adiabatic passage and multiple interactions between the laser and atom pair within one frequency-chirp. Incoherent flux enhancement during one chirp and between successive chirps is also examined.