-The present study was an effort to identify appropriate dose of mutagens for the elevation of specifi c alkaloids especially thebaine through induced mutagenesis in opium poppy (P. somniferum L.) using two stable high yielding varieties NBRI-1 and NBRI-5. Simultaneously, the study also deals correlation between cytological aberrations and their effects on alkaloid quantity. Among the two varieties NBRI-1 was more sensitive than NBRI-5. The EMS was reported most potent mutagen for creation of chromosomal abnormalities. The treatment kR 10+0.2% EMS and kR10+0.4% EMS possessed high chiasms frequency. The dose 0.2% EMS in combinations with all doses of gamma accelerates the total alkaloid as well as individual alkaloid content.