In a recent study Runyan (1983) showed the improvements of concurrent seasonal adjustment over the method of using yearly projected seasonal factors for seasonal adjustment. Twenty-seven economic time series (see Appendix) from the manufacturer's survey of value of shipments (VS), total inventories (TI), and unfilled orders (UO) were examined using X-11 and assuming a multiplicative model. Examination of plots of the series as well as subject-matter knowledge of the series led to questions concerning the validity of a multiplicative model -- which corresponds to the natural logarithm transformation. This study uses a modelling approach for estimating appropriate transformations for the series used in Runyan's concurrent seasonal adjustment study and examines whether there is substantial improvement in performing the concurrent X-11 seasonal adjustment on an optimally transformed series. We limit our attention to Box-Cox transformations of the form.