Long-range interactions can substantially modify collision or interaction p
rocesses among cold atoms. We are able to monitor their effects on two diff
erent systems: Cs atoms which undergo photoassociation and highly excited C
s Rydberg atoms. Although the length and the time scales of the interaction
s are quite different, their effects can be described with the same resonan
t dipole picture. [S0031-9007(99)08564-6].