Abstract Three new tricyclic diterpenoids margocin, margocinin and margocilin have been isolated from root bark of Azadirachtaindica and their structures established as 8,11,13-abietatrien-3,7-dione, 8,11,13-abietatrien-12,16-dihydroxy-3,7-dione and 8,11,13-abietatrien-3β,12-dihydroxy-7-one, mainly on the basis of spectral studies.