PPh3/I2 is an efficient reagent for the stereo-controlled deamination of non-activated aziridines, N–H and N-alkyl aziridines, using. The method works gives the corresponding trans-alkenes from both cis and trans-aziridines. A plausible mechanism is proposed for the ring opening and deamination of keto-aziridines in the presence of Ph3P/I2.