This paper is concerned with the experimental design for precise parameter estimation in a model of known form. Emphasis is primarily placed on three flotation models in which the parameters appear in a non-linear fashion. The first part of the paper consists of a brief statement of the statistical concepts and procedures involved in obtaining precise estimates of parameters, the logic of the design criterion, and the general sequential design procedures. Based on of this background, the second part describes the experimental design problem of estimating the parameters in three different flotation recovery models. The numbers of sampling and different measuring times for these models to obtain the precise parameter estimates are present in the conclusion. (C) 2004 Elsevier Ltd. All rights reserved.