The compound, bicyclo[4.3.0]nonane-3(4),7(8)-dicarboxylic acid and to a process for its preparation, wherein bicyclo[4.3.0]nona-3,7-diene is reacted with synthesis gas in an homogeneous organic phase in the presence of transition metal compounds of Group VIII of the Periodic Table containing complex-bound organophosphorus compounds, and of excess organophosphorus compound, at temperatures of 70 to 160° C. and pressures of 5 to 35 MPa, and the 3(4),7(8)-bisformylbicyclo[4.3.0]nonane thus obtained is oxidized, or is first hydrogenated to 3(4),7(8)-dihydroxymethylbicyclo[4.3.0]nonane and the diol thus obtained is reacted in an alkali melt.