Background There is a long term interest in running the fission reaction backwards, i.e., studying the "inverse fission" of uranium. The recent availability of beams of n-rich fission fragments has stimulated interest in this endeavor.Purpose To search for inverse fission in the reactions 124,132 Sn + 100 Mo.Method In the 124 Sn + 100 Mo reaction, evaporation residues were searched for using in beam detection of evaporation residues, in beam α-spectroscopy, and post-irradiation alpha spectroscopy while in the 132 Sn + 100 Mo, the evaporation residue, 230 U, was searched for using post irradiation alpha spectroscopy.Results No evidence for the occurrence of the "inverse fission" reactions was found. The upper limit cross section for the latter reaction is ∼ 550 µb, while the experimental upper limit cross section for the former reaction is about 21 +38 −21 nb. ConclusionsThe intensity of suitable radioactive beams is not high enough at present to detect inverse fission. For the 124 Sn + 100 Mo reaction, the observed upper limits are below the estimates of current models for these reactions, probably due to fusion hindrance.