In male chinchillas of commercial flocks fertility demographic indexes were studied in order to asses its reproduction capacity. The data were obtained from the registries of two commercial flocks of the Metropolitan region of Chile. These flocks were very similar in their management. The mean general rase fertility was 3.06 live births by male in a year. The greatest speciflc fertility rase was observed in animals aged from 1.5 to 5.5 years. The total fertility rate showed that the mean offspring of a mate chinchilla was 51 live births during his life, 27 of them were male live births. The sex rase at birth was 111 males by 100 females and the sex rate during the reproduction age was 59 males by 100 females.En chinchilla de criaderos se obtuvieron indicadores demográficos de fecundidad en el macho con el objeto de evaluar su capacidad de producir descendientes vivos.Se trabajó con la información contenida en los registros de dos criaderos de la región Metropolitana de Chile, semejantes en su manejo general.La tasa de fecundidad masculina general fue de 3,06 crías vivas por cada macho en edad fér­til. La mayor fecundidad la presentan los machos entre las edades de 1,5 y 5,5 años. Durante su vida reproductiva el macho tiene una descendencia de 51 crías de los cuales 27 son machos. La razón de masculinidad al nacimiento es de 111 machos por 100 hembras y durante la edad reproductiva es de 59 machos por 100 hembras.