Konno and Inori (1989) have recently proposed two flexible models for bond portfolio optimization, together with heuristics to solve them. It is shown that substitution of products of variables or linear expressions by new variables allows the reduction of the two models to a hyperbolic and a bilinear program respectively. The size increase is small and exact methods to solve the resulting problems are available. It is also shown that more general models in which the objective function is a product of linear or bilinear functions can be reduced to bilinear programs in a similar way.