We compute the strangeness-conserving double beta decay of Σ- hyperons, which is the only hadronic system that can undergo such decays. We consider both, the lepton number conserving Σ- → Σ+e-e-νν (ββΣ2ν) and the lepton number violating Σ- → Σ+e-e- (ββΣ0ν) modes. The branching ratios of these ββ decays are suppressed at the level of 10-30 considering a light neutrino scenario in the case of the ββΣ0ν channel. The dynamical origin of such low rates and their possible enhancements are briefly discussed. Given its simplicity those decays can be used also for the purposes of illustrating the main features of double beta decays.Facultad de Ciencias Exactas