In order to achieve higher efficiency in use of materials and energy when providing a service or functionality of a product, indicator values can be used to point out the direction of development. The objective of the present study is to assess temporal variations of inventory data and identify significant environmental impacts for a product by using a life cycle assessment (LCA) approach. The study was restricted to a gate-to gate analysis of a Swedish manufacturer of NiCd batteries during the period 1983-1998. Inputs and outputs of materials and energy were compiled from environmental reports, which were related to the volume of produced batteries. The environmental impact was assessed by evaluation with different characterisation and weighting indices. The characterisation results regarding potential impact in resource use, global warming potential, acidification, eutrophication and aquatic ecotoxicity showed an average decrease of 2- 6 times during the period studied. The results of weighting showed that the environmental impact differed in the range -48 to 91 % per year according to the methods of ECO, ET, EDIP and EPS. The temporal variations of the results show the importance of choosing representative inventory data when making a LCA. Major reasons for the reduction in environmental impact were due to increased production meanwhile reducing dissipative emissions of metals. Evaluation with environmental indices is a great simplification of reality but it can help to identify significant environmental impacts of a product.