The effects of burial maturation upon seven molecular maturity parameters, and the concentrations of individual biomarkers employed in these parameters, have been studied in a well in the Barents Sea. The depth interval between 1400 and 3000m comprises homogenous Eocene claystones with effectively uniform organic carbon content (0.4–0.6%) and kerogen type (HI of 100–200mg HC/g TOC). The quantitative biomarker data thus contain minimal interference from organic facies, hydrocarbon expulsion effects and the presence of migrated hydrocarbons. Bulk geochemical data define the hydrocarbon generation threshold (or “oil window”) at around 2300m. Molecular maturity parameters proceed to equilibrium, and in some cases demonstrate inversion at high maturity. These molecular changes are associated with major changes in biomarker concentrations. The %ββ hopane, %22S C 31 αβ hopane and %20S C 29 ααα sterane parameters proceed as a result of the balance between the relative rates of generation and thermal degradation of the different isomers. Increased concentrations of the individual isomers are interpreted to be the result of biomarker generation from the kerogen (mainly) and other macromolecular/polar fractions. The %αββ C 29 sterane parameter and the three parameters involving rearranged hopanes (%Ts, %29Ts and %diahopane) operate at higher maturity levels, and proceed as a result of the relative rates of thermal degradation of the compound pairs. Isomerisation in the bitumen may also influence the operation of the parameters involving stereoisomers, but must be a relatively minor contribution.