The adsorption and UV photochemistry of 1,3-butadiene (CH2=CHCH=CH2) on highly oriented pyrolytic graphite (HOPG(0001)) was studied using temperature-programmed desorption (TPD) and electron energy loss spectroscopy (EELS). Butadiene physisorbs on HOPG with the monolayer exhibiting first-order desorption kinetics and a corresponding desorption energy of 32 kJ/mol. The multilayer exhibits zero order desorption kinetics with a desorption energy of 28.5 kJ/mol. Irradiation of the C4H6/HOPG(0001) adlayer (one and three monolayers (ML) Of C4H6) with UV photons at 193, 248, and 351 nm and fluences of up to 100 mJ/cm(2). pulse resulted in molecular photodesorption. Photodesorption was described by a laser-induced thermal desorption process as supported by simple calculations of the surface temperature rise. The photoprocesses occurring in both 1 and 3 ML C4H6 adlayers on HOPG(0001) were also investigated at incident powers of less than or equal to 10 mJ/cm(2).pulse. Under these conditions, there was no detectable photodesorption or condensed phase photochemistry at any of the wavelengths investigated.