The heat of adsorption of naphthalene on Pt(111) at 300 K was measured with single-crystal adsorption calorimetry. The heat of adsorption on the ideal, defect-free surface is estimated to be ( 300 - 34 Theta -199 Theta(2)) kJ/mol. From this, a C-Pt bond energy for aromatic hydrocarbons on Pt( 111) of similar to 30 kJ/mol is estimated, consistent with earlier results for benzene on Pt( 111). There is higher heat of adsorption at very low coverage, attributed to step sites where the adsorption heat is >= 330 kJ/mol. Saturation coverage, Theta = 1 ML, corresponds to 1.55 x 10(14) molecules/cm(2). Sticking probability measurements of naphthalene on Pt( 111) give a high initial value of 1.0 and a Kisliuk-type coverage dependence that implies precursor-mediated sticking. The ratio of the hopping rate to the desorption rate of this precursor is similar to 51. Naphthalene adsorbs transiently on top of chemisorbed naphthalene molecules with a heat of adsorption of 83-87 kJ/mol.