This paper reports the results of a study of arthropod remains from an organic deposit located between tills of the Last Glacial Maximum and the Younger Dryas glaciations, at Croftamie in the type area of the Loch Lomond Readvance in western central Scotland. The arthropod fauna shows that the organic deposit was laid down in a shallow freshwater pool surrounded by moss and leaf debris. Quantified palaeotemperature estimates made using the Mutual Climatic Range method on the coleopteran assemblage show that the climate was severe with mean annual temperatures of about −5°C, and by reference to a previously derived radiocarbon date, this temperature is ascribed to the period around 10 560 ± 160 14C years bp. The results from Croftamie are compared with other sites from Britain and Ireland and it is demonstrated that the Loch Lomond glacier reached its limit at about the middle of the Younger Dryas cold period. The age estimates derived by calibration of the radiocarbon ages may suggest earlier glacier expansion and that the lower boundary of the Younger Dryas in Britain may have been misplaced in the radiocarbon timescale.