This paper uses a new data set on innovation output to assess the degree to which the level of innovation in manufacturing firms is influenced by firm size and firm age. Indicators of innovation output used are the number of new products introduced as a function of firm sales and the proportion of firm sales obtained from products first introduced in the previous five years. While the evidence is mixed, the results tend to indicate that it is possible to separate the effects of age and size in assessing the level of innovation. Both firm size and firm age tend to be inversely related to innovative output.