Two 8-carboline lactams harmalanine and harmalacidine have been isolated from the seeds of Peganum harmala and their structures were elucidated as I and I1 respectively through chemical and spectroscopic studies. In the case of I, which is the simplest tetracyclic B-carboline lactam from any source, detailed nmr ('H and 13C) investigations including noe difference. 2D nmr (cosy-45, noesy, 3-resolved) double resonance experiments and lH-'3~-hetero-~~~~ measurements have been used.