Laurocerasus officinalis Roem. (Prunus laurocerasus L.), also locally known as "karayemis or taflan", is a popular black summer fruit belonging to the genus Prunus and the family Rosaceae. L. officinalis exhibits numerous biological activities, such as anti-inflammatory, antinociceptive, antioxidant, neuroprotective, and antidiabetic effects. The aim of this study was to determine the total phenolic content and cytotoxic effect of dimethyl sulfoxide extract of L. officinalis (DEL). The total phenolic content and cytotoxic effect of DEL were investigated using the Folin-Ciocalteu method and thiazolyl blue tetrazolium bromide (MTT) assay, respectively. Total phenolic content value was 33.7 +/- 0.13 mg gallic acid equivalent per g sample. DEL exhibited selective cytotoxic effects against four human cancer (lung, colon, liver, and cervix) cell lines. The most selective cytotoxic effect of the extract was observed in colon cancer cells (IC50 = 265.2 +/- 8.1 mu g/mL) compared to normal fibroblast cells. These data demonstrate that L. officinalis extract exhibits selective cytotoxicity towards some cancer cells. Further studies are now needed to clarify the molecules involved and their mechanisms.