The Bivak cave is a cavern of small dimensions on the west slope of the Pilis mountain, north-west of Budapest. The excavation was conducted by D. Jánossy and L. Vértes in the autumn of 1953. The sequence of the Pleistocene layers are the following from the top downwards: 1. a yellow layer, 2. beneath that, in some places one of orange colour, 3. a yellowish grey one, 4. a grey, and 5. a reddish brown one. The cave has yielded a very rich fauna, well dividable by the layers, as well as a few but interesting archaeological finds (PI. I). According to the examination of S. Kretzoi-Varrók the cave-bear has been dominating in the two lower layers. From the yellowish grey layer upwards it decreases rapidly and the hare (Lepus timidus) has taken the leading part and besides it the characteristical species of polar tundra and steppe. The climatic changes which could be concluded from the aforementioned facts are proved by the micromineralogical examination of M. Herrmann, according to which the limonite as well as the magnetite have been dominating in the two lower layers, and the heavy fraction showing to originate from the loess in the upper ones. L. Vértes carried out petrographical examinations on the material of the layers which prove - strictly parallel with the aforementioned results - that the fifth layer was deposited at the extreme end of Würm I according to the astronomical theory of Milankovitch-Bacsák. The grey layer represents the oceanic tundra phase initiating the Würm I/II interstadial. Presumably there was a breaking off in the sedimentation. The layer of orange colour and the yellow one indicate the Würm II and III stadials which cannot be separated in Hungary, as it is proved by the examination of our deposits. The upper level of the former streches into the postglacial time. The author gives the absolute dates - according to Milankovitch - of the age of the layers.