The polynomial growth curve model based on the multivariate normal distribution has dominated the analysis of continuous longitudinal repeated measurements for the last 50 years. The main reasons include the ease of modelling dependence because of the availability of the correlation matrix and the linearity of the regression coefficients. However, a variety of othPI useful distributions also involve a correlation matrix: the multivariate Student t, multivariate powPI-pxponential, and multivariate skew Laplace distributions, as well as Gaussian copulas with arbitrarily chosen marginal distributions. As well, with modern computing POWPI and software, nonlinear regression functions can be fitted as easily as linPM ones. By a number of pxamples, we show that these distributions, combined with nonlinear regression functions, generally yield an improved fit, as compared to the standard polynomial growth curve model, and can provide diffpxent conclusions.