Hydrogen sulfide (H2S) is an endogenously-produced gaseous second messenger that can regulate many physiological processes. Diallyl trisulfide (DATS) is an organic polysulfide compound found in garlic that acts as an H2S donor. It reduces the survival of prostate cancer PC-3 cells (IC50 = 22 μM) and inhibits the growth of human colon adenocarcinoma HCT15 cells (IC50 = 11.5 μM). DATS suppresses the growth of PC-3 xenografts in vivo in mice and induces vascular smooth muscle relaxation. Garlic extracts also lower cholesterol and there is evidence that DATS can alter the expression of genes and inhibit enzymes that are relevant to cholesterol synthesis.