This paper presents a preliminary analysis of the fecundity-length relationship of the North Sea mackerel. The relationship was compared to that of the Western mackerel stock (LOCKWOOD,1978) by an analysis of covariance between the regression lines. Further analysis is necessary before any decisive conclusion can be drawn. The results, however, seem to demonstrate a lower fecundity in the North Sea mackerel (140 000 - 360 000 eggs) as compared to the Western mackerel (400 000 - 990 000 eggs) at the same range of length. A comparison of regression lines of fecundity-length for the North Sea and the Western area shows a significant difference between the two lines.