Résumé : In an experiment using a heavy liquid bubble chamber the Ξ hyperon lifetimes and α parameters were measured to be τΞo = (3.04 ± 0.230.26) × 10-10 sec, τΞ- = (1.73 ± 0.070.08) × 10-10 sec, αΞo = -0.84 ± 0.27 and αΞ- = -0.42 ± 0.11. These values agree with measurements which employed different techniques and are consistent with the predictions of the ΔI = 1 2 rule. © 1972.