A systematic study has been carried out in order to investigate the possibility to grow ultrathin organic films by self-assembly on pyrite (FeS2) from solutions of triphenylphosphine, n-alkanethiols and n-alkylamines. The adsorption of the different molecules on pyrite(100) surfaces was studied with regard to chemical composition using X-ray photoelectron spectroscopy and with regard to molecular orientation by near-edge X-ray absorption fine structure and IR spectroscopy. Triphenylphosphine readily adsorbs from a solution in ethanol and forms dense monolayers. The adsorption of n-alkylamines is found to result in the formation of highly oriented films. n-alkanethiols, which form well defined monolayers on Au, Ag and Cu surfaces are not found to adsorb on pyrite from solutions in ethanol.