The effect of strigolactones on plants, which has been recently described as a new group of plant hormones, has not been fully characterized. Capparis spinosa L. callus formation using synthetic strigolactone GR24 (0.1 and 0.2 mu M) alone or combined with 1-naphthalene acetic acid (NAA) (10.74 mu M) and 6-benzylaminopurine (BAP) (4.44 mu M) and its effect on phenolic compounds production were evaluated. Compared to the other media, the media with 10.74 mu M NAA + 4.44 mu M BAP + 0.1 mu M GR24 or 10.74 mu M NAA + 4.44 mu M BAP gave the highest callus formation. The highest rutin, quercetin and chlorogenic acid content were found in a medium with 10.74 mu M NAA + 4.44 mu M BAP + 0.1 mu M GR24. Aromatic compounds in caper calluses were grouped as sulfur compounds (66.97-87.53%), aldehydes (4.88-7.90%), ketones (0.34-19.3%), hydrocarbons and derivatives (0.56-5.8%), alcohols (1.62-6.08%), others (0.61-2.37%) and their amounts varied at various hormone applications. When 0.2 mu M GR24 was applied solitarily, the total sulfur compound in callus samples was 87.53% and the dominant compound was found to be methyl isothiocyanate. These results suggested that GR24 may be effective in the accumulation of chlorogenic acid, rutin and quercetin phenolics in caper callus culture.