The Weibull distribution was successfully used to describe the diameter distribution of poly(N-isopropylacrylamide-co-methacrylic Acid (PNIPAAm-MAA) nanoparticles, whereas the lognormal was deemed not adequate for that purpose. The method of moments was used to predict parameters of the Weibull distribution. In this approach, the Weibull parameters were recovered from the diameter mean and variance, both of which were predicted from temperature. The distributions predicted from various temperatures for both MAA/NIPAAm ratios of 0.05 and 0.10 showed trends similar to those displayed in the observed data. (c) 2008 Wiley Periodicals, Inc. J Appl Polym Sci 111: 2584-2589, 2009