The micro-structure of an atmospheric pressure, opposed flow, methane diffusion flame has been studied using heated micro-probe sampling. Mole fraction profiles of major products as well as trace aromatic, substituted aromatic, and polycyclic aromatic hydrocarbons (PAH up to C16H10, e.g., pyrene) were quantified by direct gas chromatography/mass spectrometry (GC/ MS) analysis of samples withdrawn from within the flame without any pre-concentration. Mole fractions range from 0.8 to 1.0 x 10(-7). Soot volume fraction and number density profiles were also determined with the use of classical light scattering techniques. Soot volume fraction and number density ranged from 4.0 x 10(-9) to 1.4 x 10(-8) and 1.0 x 10(17) to 3.0 x 10(19) m(-3), respectively. These results should provide useful information for the development and verification of detailed chemical kinetic models aimed at the formation and destruction of PAHs and soot.