Comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC x GC-TOFMS) was used to identify methylhopanes in oils. 2 alpha Methyl-17 alpha(H),21 beta(H)-hopane and 2 alpha-methyl-17 beta(H),21 alpha(H)-hopane (2 alpha-methylhopane) series were found in oils from Cear Basin, Brazil. In the 3 beta-methylhopane series, only C-31 3 beta-methyl-17 alpha(H),21 beta(H)-hopane was detected. In addition, a novel terpane series (C-30-C-34), which eluted after the regular hopanes (comparing compounds of both families with the same carbon number) either in 1D (first dimension) or 2D (second dimension), was identified. A compound likely to be bisnorgammacerane was separated from C-29 25-norhopane in the 2D, and consequently identified. An unusual compound pair eluting after the C35R moretane was tentatively identified as C-36 17 alpha(H),21 beta(H)-homohopanes (22S, 22R). The presence of 2 alpha-methylhopanes in oils from Cear Basin may indicate oxygen-producing cyanobacteria were important biological inputs in the deposition environment. This is the first study that shows the separation between hopane and 2 alpha-methylhopane series and their tentative spectral identification using GC x GC-TOFMS, as they are usually not well separated in one-dimensional gas chromatography.