The three K-star components of the 36 Ophiuchi system have been analyzed in detail on high resolution, high S/N ESO Reticon spectra. The atmospheric parameters of the stars (effective temperature, spectroscopic gravity, microturbulence, metal abundances, and degree of chromospheric activity) have been determined. The position of the observational ZAMS built up by the three stars has been compared with theoretical ZAMS. The agreement between the iron abundances is excellent for the three components. A discussion of the masses of the components is also given.