1. A detailed study was made of the subsequent stages in the colour change of the Stoat, Mustela erminea Linnaeus, 1758. 2. Starting and finishing date of both Autumn and Spring moult were determined, based on the examination of 300 pelts from the Netherlands. 3. An indication was found for the existence of a difference in finishing date of the Spring moult in male and female Stoats. The examinations showed that female Stoats complete their summercoat a good month earlier than males. 4. It appeared that there is a remarkable difference in number of completely white animals between warmer and colder parts in the Netherlands. The colder regions hold much more completely white animals. This indicates that temperature has an influence on whether Stoats turn completely white or have a variegated wintercoat.