A process for filling pharmaceutical product containers in a container filling machine with the stages of: filling the container with the corresponding pharmaceutical substance through filling means in a filling station of the filling machine, weighing the filled container in a filled container weighing station to confirm that the quantity of pharmaceutical substance with which the container has been filled lies within the desired range, in which when the quantity of pharmaceutical substance with which the container has been filled lies outside the desired range the filling means are moved to the filled container weighing station and the container is topped up with a quantity such that the total substance placed in the container in the two stages lies within the desired range.
