In this study we report the cytotoxic effect on human cancer cells of two series of novel progesterone derivatives; the first containing an aromatic ester (8a-e) or a carbamate functions both linked to C-3 (9a-e) on the pregn-4,16-diene-6,20-dione skeleton. In the second series, both functional groups (ester and carbamate) are bound to C-17 on the pregn-4,6-diene-3,20-dione scaffold (13a-e and 14a-e). The panel cancer cell lines used in this study were the following: PC-3 (human prostate cancer cell line), MCF-7 (human breast cancer cell line), HCT-15 (human colon cancer cell line) and J774 (noncancerous murine macrophages) for comparison. The results from this study showed that steroid 14a, having a carbamate function at C-17, was the most potent against PC-3 cell line (96.6%) while 8c and 8e showed much higher cytotoxic activity (100%) for MCF-7 cell line. Finally, compounds 8c and 14a displayed selective properties towards tumor cell lines than noncancerous murine macrophages.