The caecotrophy rhythm of 15 male rabbits was registered continuously for 320 days at 5 different LD schedules (LD 12:12, LL, LD 23:1, LD 11:1 + 11:1, LD 12:12). The results were compared with the preceding experiment of the reverse set‐up. The following results were obtained:1.The caecotrophy rhythm, biphasic during LD 12:12, ran free mono‐phasically in all animals.2.Aftereffects of the preceding LD 12:12 were present for up to 52 days, affecting the length of the free‐running period significantly.3.The insertion of the 60‐minute scotoperiod schedule was responded by delay shifts, the signal meeting the free‐running rhythm during the early subjective night, and by advance shifts, when the signal occurred during the late subjective night.4.Eight animals did entrain with the 60‐minute scotoperiod. The average phase angle difference was negative; both the interindividual and intra‐individual scatters were very high.5.Seven animals did not entrain with the LD 23:1 but exhibited an oscillatory free‐run.6.During the skeleton scotoperiod only 6 animals showed stable entrainment, 9 animals failed to entrain with this Zeitgeber.7.The comparison of the phase angles during the 60‐minute scoto‐ and photoperiod experiments, the respective skeleton‐photoperiod experiments and the complete LD 12:12 schedules indicates that the phase angle difference becomes more negative at an increasing LD ratio in the rabbit.8.The results suggest that a sceleton photoperiod is nearly as strong a Zeitgeber as a complete LD 12:12 and that Zeitgeber strength decreases from LD 1:23 to LD 23:1 to LD 11:1 + 11:1.9.The oscillatory free‐run can be explained reasonably on the assumption of a more pronounced delay section of the phase response curve in these rabbits.