Published procedures for mixture experimentation in the presence of process variables arc reviewed. Procedures which inscribe figures in the mixture space result in lower numbers of experiments but are limited because they do not permit full exploration of the mixture space. In this paper, alternative procedures which minimize the loss of the mixture space are presented. Eight cases representing all combinations of the following are considered: three and four mixture variables, with and without a center point of interest in the mixture space, and with and without constraints on compositions. Solutions are lists of coordinates of the vertices of the cuboidal regions inscribed in the mixture space. Transformations which facilitate linking the mixture space with the factor space of the independent variables are also presented.