The study was carried out to develop maturity indices for seeds of four important multipurpose tree species in North India viz. Acacia catechu Willd., Acacia nilotica Willd., Albizia lebbeck Benth., and Tectona grandis L. We suggest that a composite seed harvest index that combines several fruit and seed parameters may be a useful in predicting better seed germination in the species studied. Thus, for achieving maximum seed quality, seeds of A. catechu should be harvested during the second week of January when the seed and pod moisture is 20-23%, 100-pod weight is approximately 23 g, and the seed colour changes from greenish-brown to light brown. The best period for harvesting good quality seeds of A. nilotica is the second fortnight of June when the pod and seed moisture is 5-6% and 100-pod weight is approximately 6 g. A. lebbeck pods should be collected during the last week of February when the seed and pod moisture is approximately 10%, 100-pod weight is approximately 10 g, the pods have not yet started to split, and the seed colour changes from light brown to dark brown. In T. grandis the suitable period for fruit harvest is the first fortnight of March when the 100-fruit weight is between 35-40 gm, the fruit moisture is approximately 14%, and the fruits become lighter in colour.