Parameter estimates of the von Bertalanffy growth function (VBGF) and its inverse function, based on length-at-age and age-at-length data for Tilapia rendalli (Cichlidae) and Salmo trutta (Salmonidae) were derived using a variety of "direct" and "indirect" fitting methods. The results obtained by different fitting methods are similar, except when the obvious is ignored: the data must cover the same range of lengths and ages and their weighting factors must be the same.