A review. A substantial body of literature exists on the issues of optimization and scaling in HPLC. However, much of this literature is written in a theor. manner such that it is difficult for the practicing chromatographer to apply the conclusions to problems in the laboratory In addition, the analyst would have to search numerous publications to find all of the formulas that are needed when optimizing or scaling a method. In this review, an attempt is made to address these topics in a manner that is easy to follow, with all equations given in the form that is most convenient for the laboratory chemist, and with all necessary formulas available in a single source. The focus of the review is on the math. concepts relevant to optimization and scaling. Issues that are generally not approached math., such as the selection of the mobile phase and stationary phase, are not discussed.