AbstractThe isomeric lactams benzo[b]phenanthridine‐5(6H)‐one and benzo[j]phenanthridine‐6(5H)‐one were obtained in equal yields by Schmidt reaction on 11H‐benzo[b]fluoren‐11‐one (44% total) or by Beckmann reaction on 11H‐benzo[b]fluoren‐11‐one oxime (22% total). Reduction of the lactams with lithium aluminum hydride gave the 5, 6‐dihydro‐benzo[b]‐ and ‐[j]phenanthridines. Dehydrogenation of these dihydro derivatives produced the parent aromatic heterocycles benzo[b]‐ and benzo[j]phenanthridine in best overall yields of 20% and 12%, respectively. A few substituted benzophenanthridines were also prepared. Assignment of structures was based on ultraviolet, infrared, and n.m.r. spectra of the dihydro derivatives as well as on separate unequivocal synthesis of the