Huntington's disease is an autosomal dominant inherited disorder, caused by an expanded polyglutamine region of a protein called huntingtin with unknown function. Transgenic mice expressing the N-terminal of huntingtin, containing 82 glutamines, exhibit a progressive disorder, which resembles to the human disease. In this study, we tested the longitudinal behaviour changes in this transgenic line in open-field and elevated-plus-maze tests. The motor performance deteriorated at 12 weeks of age and the disease progressed as indicated by the decreased total distance covered, the decreased mean velocity and the decreased exploratory behaviour. The level of anxiety was unchanged in transgenic mice as compared with their littermate controls. The motor deterioration was similar to that in other Huntington's disease models, while the level of anxiety was different. These tests are suitable means of following the progression of the disease and useful for studies of the effects of therapeutic interventions.