Ten lots of Fuenzalida & Palacios type antirabies vaccine for human use, produced at the Instituto Butantan (São Paulo, Brazil) were stored at temperatures of 45, 37, 28 and 2-8ºC. The potency of each lot was determined in samples taken at varied time intervals using the NIH method and lots presenting antigenic values > 0,3 were considered satisfactory for use. After 2 hours at 45ºC the antigenic value of one out of 10 lots tested was found to be less than the minimum required value. At 37ºC all lots maintained satisfactory antigenic values until the third day of storage, whilst at 28 and 2-8ºC the potency was fully maintained, respectivelly for 10 and 360 days. At the ideal temperature of 2-8ºC, 100% of the tested vaccines maintained the minimum required antigenicity for a longer period (16 months) than the expiry time of 6-12 months usually recommended for this type of biological produced in Latin American and Caribbean countries. Thus, the obtained data suggested that in countries still producing Fuenzalida & Palacios type vaccine, the expiry time could be extended to 16 months, what could prevent the unnecessary discarding of products still in useful condition.