In order to study the formation of carbonaceous solid deposits from aviation fuels in the pre-combustion environment of next-generation high-speed aircraft, we have pyrolyzed the model fuel n-decane (critical temperature, 344.5 degrees C; critical pressure, 20.7 atm), an alkane component of jet fuel, under supercritical conditions at 570 degrees C, 100 atm, and 133 sec. The product polycyclic aromatic hydrocarbons (PAH), precursors to the solid deposits, have been analyzed by a two-dimensional high-pressure liquid chromatographic separation technique with ultraviolet-visible absorbance and mass spectrometric detection. The analyses reveal that there are 24 unsubstituted PAH products with molecular weights between 252 and 300. Of these, 12 are benzenoid: benzo[a]pyrene, benzo[e]pyrene, perylene, benzo[ghi]perylene, anthanthrene, benzo [b]chrysene, dibenz[a,c]anthracene, dibenz[a,h]anthracene, dibenz[a,j]anthracene, pentaphene, picene, and coronene; two are methylene-bridged derivatives of two of the benzenoid PAH: 11H-indeno[2,1,7-cde]pyrene and 4H-benzo[def]cyclopenta[mno]chrysene; five are fluoranthene benzologues: benzo [a] fluoranthene, benzo[b]fluoranthene, benzo[j]fluoranthene, benzo[k]fluoranthene, and indeno[1,2,3-cd]pyrene; and five are fluorene benzologues: dibenzo[a,h]fluorene, dibenzo[a,i]fluorene, naphtho[1,2-a]fluorene, naphtho[1,2-b]fluorene, and naphtho[2,1-a]fluorene. Eighty-three alkylated derivatives of these PAH have also been identified as products of n-decane pyrolysis. Fourteen of the unsubstituted PAH and all of the allcylated derivatives have never previously been identified as products of n-decane pyrolysis or combustion. The UV spectra establishing the identities of the 24 unsubstituted n-decane pyrolysis products are presented.