In the light of the potential application of these ubiquitous proteins in cancer therapy, this study was undertaken to characterize nine new non-larvicidal and non-hemolytic Bt isolates collected from various regions in Saudi Arabia according to: (i) colony and crystal morphology, (ii) protein profile of the crystalline parasporal inclusions, (iii) screening for presence of Cry, Cyt and PS genes by PCR, (iv) screening for in vitro cytotoxic activities against two selected cancerous cell lines; viz., colon (HT-29) and cervical (HeLa), and (v) mechanism of killing. The gene discussed is CRYL1; the disease is cancer.