At Kollsete 380 m a. s.l., Sogndalsdalen, a 20 cm thick bed with gyttja silt has been recorded beneath 3 m glaciolacustrine silt and 5-6 m till deposits. The gyttja silt is supposed to have been deposited during the initial phase of a glacial lake located laterally to an advancing valley glacier. The sedimentation of the gyttja silt was succeeded by the deposition of a glaciolacustrine silt and a lodgement till. The pollen assemblage in the gyttja silt reveals open, treeless vegetation. An Arctic/alpine climate is confirmed by the insect fauna and plant macro fossils. Two radiocarbon age estimates of the gyttja, > 39 200 BP and 43 800 BP, indicate an interstadial of Mid Weichselian age. Correlations with the Bø interstadial (about 40-60 ka BP), and Sargejokha interstadial (35-60 ka BP) are suggested.There is also a discussion of correlations with other Mid Weichselian localities.