Abstract: Method and device for monitoring the validity of at least one parameter which is calculated by an anemometeric unit of an aircraft. The device (1) includes means (13) for taking into account n first data, each dependent on said parameter being monitored, n being greater than or equal to 1, means (15) for taking into account p second data, p being greater than or equal to 2, each of which depends on at least one value obtained from at least one data source (Si) external to said anemometeric unit (2), means (18) for calculating, for each of the second data, a difference between this second datum and a first datum of the same type, means (21) for comparing the absolute value of each of said differences with a threshold value, and means (23) for deducing from said comparisons that said parameter is invalid if the absolute values of at least two of the various differences are greater than the corresponding threshold values.