Many operations research problems can be modelled as the transportation problem (TP) or generalized transportation problem (GTP) of linear programming together with parametric programming of the rim conditions (warehouse availabilities and market requirements) and/or the unit costs (and or the weight coefficients in the case of the GTP). The authors have developed an operator theory for simultaneously performing such parametric programming calculations. The present paper surveys the application of this methodology to several classes of problems: (a) optimization models involving a TP or GTP plus the consideration of an additional important factor (e.g., product ion smoothing, cash management); (b) bicriterion TP and GTP (e.g., multimodal TP involving cost/time trade-offs, TP with total cost/bottleneck time trade-offs); (c) multi-period growth models (e.g., capacity expansion problems); (d) extensions of TP and GTP (e.g., stochastic TP and GTP, convex cost TP); (e) branch and bound problems involving the TP or GTP as subproblems (e.g., traveling salesman problem, TP with quantity discounts); and (f) algorithms for solving the TP and GTP (e.g., a polynomially bounded primal basic algorithm for the TP, a weight operator algorithm for the GTP). The managerial and economic significance of the operators is discussed.