With the help of column chromatography, 3 new substances, 1-exo,4,5,7,8,8- hexachloro-3a,4,7,7a-tetrahydro-4,7-methanoindene 1-exo,2-exo,4,5,7,8,8- heptachloro-3a,4,7,7a-tetrahydro-4,7-methanoindane, and 1-exo,2-exo,4,6,7,8,8-heptachloro-3a,4,7,7a-tetrahydro-4,7-methanoindane, were isolated from technical chlordane and were identified by spectroscopic methods (mass spectrometry, infrared, and 1H NMR). These compounds could be synthesized by photochemical dechlorination of heptachlor and of α- (or cis-) chlordane in methanol. In addition, the mixture was investigated by capillary gas chromatography and by combined gas chromatography and mass spectrometry. The data obtained were used to characterize the composition of technical chlordane.