We apply Megiddo's parametric searching technique to several geometric optimization problems and derive significantly improved solutions for them. We obtain, for any fixed e > 0, an O(n 1+~) algorithm for computing the diameter of a point set in 3-space, an O(s/5 +~) algorithm for computing the width of such a set, and an O(n s/s +~) algorithm for computing the closest pair in a set of n lines in space. All these algorithms are deterministic.