Cones and seeds of conifers, such as Pinus roxburghii, P. wallichiana, P. gerardiana, Cedrus deodara, Abies pindrow and Picea smithiana are seriously damaged by Dioryctria abietella Denis and Schiff. (Lepidoptera : Pyralidae) in the North-Western Himalayan region of India. Bioecological studies carried out during 1991 - '92 revealed that the females laid whitish, elliptical eggs singly on the depressed surface of the young cones. The average egg size was 1.00 ± 0.11 x 0.60 ±0.08 mm and this stage lasted for 3 - 5 days. The larval stage passed through five instars. All the instars differed in appearance, size and duration and larvae became full-fed in an average of 24.8 ± 1.9 days. The full-fed larva spun a cocoon around itself, sealed it with white papery membrane and pupated inside the cone or any other outside protected place. The prepupal and pupal periods lasted for 7-8 and 10-14 days, respectively. The pupa was dark brown, 13.8 ± 0.07 mm in length. Total period from egg to adult varied from 46 to 59 days (52.7 ±4.8 days). Adults were dirty brown in appearance and were 13.59±0.115 mm long with an average wing expanse of 29.0 ± 1.00 mm. They lived for 4 to 5 days. Under laboratory conditions, the pest completed two generations per year and full-fed larvae of 3rd generation overwintered during September - October. Two larval parasites belonging to order Hymenoptera and Diptera, and a fungal pathogen (Fusarium sp.) were found associated with this pest. The detailed biology, nature and extent of damage, along with its distribution have been discussed and methods of control suggested.