The aim of this research was to determine the sample size (number of fruits) needed to estimate the average of Royal Gala and Fuji apples characters, evaluated at harvest and postharvest, after a period in cold storage. In Royal Gala and Fuji apples were measured eight characters at harvest and 11 after could refrigeration. For each character in each cultivar, measured at harvest and after cold storage, was calculated the mean, variance, coefficient of variation, skewness, kurtosis and checked the normality and, then, was calculated the sample size. Larger sample sizes are needed to estimate the average of: ethylene production, ratio, respiration, weight and acidity. Smaller sample sizes are needed for the measurement of longitudinal diameter, pulp firmness, total soluble solids, transversal diameters (major and minor) and juice content. The sample size required to measure the characters of Royal Gala apples is lower than that required for Fuji apples. In Royal Gala and Fuji apples, 88 and 190 fruits, respectively, are sufficient for the measurement of characters, at harvest and after cold storage, with estimation error of 5% of the average. Key words: Malus domestica, sampling, experimental design, post-harvest. O objetivo deste trabalhofoi determinar o tamanho de amostra (numero de frutos) necessario para a estimacao da media de caracteres de macas Royal Gala e Fuji, avaliados na colheita e pos-colheita, apos periodo sob armazenamento refrigerado. Em frutos de macieira Royal Gala e Fuji, foram mensurados oito caracteres na colheita e 11 caracteres apos armazenamento refrigerado. Para cada caractere mensurado em cada cultivar, na colheita e apos o armazenamento refrigerado, foram calculados a media, a variancia, o coeficiente de variacao, a assimetria, a curtose e verificada a normalidade e, em seguida, calculado o tamanho de amostra. Maior tamanho de amostra e necessario para a estimacao da media de: producao de etileno, ratio, respiracao, massa e acidez titulavel. Menor tamanho de amostra e necessario para a mensuracao de: diametro longitudinal, firmeza de polpa, solidos soluveis totais, diametros transversais (maior e menor) e teor de suco. O tamanho de amostra necessario para a mensuracao de caracteres de macas Royal Gala e menor em relacao ao necessario para macas Fuji. Em macas Royal Gala e Fuji, 88 e 190 frutos, respectivamente, sao suficientes para a mensuracao de caracteres na colheita e apos o armazenamento refrigerado, com erro de estimacao de 5% da media. Palavras-chave: Malus domestica, amostragem, planejamento experimental, pos-colheita.