Whether or not concrete prism tests developed for assessment of alkali-silica reactivity of aggregates might be suitable for general ASR performance testing of concrete has been evaluated. This paper discusses how variations in specimen pre-treatment, ASR exposure conditions and prism size influence the rate and amount of alkali leaching and prism expansion, together with a discussion of consequences for ASR test procedures. Furthermore, results from some complementary tests are included. Generally, a remarkably high proportion of the in-mixed alkalis were leached out of the concrete prisms during the ASR exposure. For prisms exposed to 60 C, the rate and amount of alkali leaching is the main controlling factor for the prism expansion. For less permeable concretes exposed to 38 C, lack of internal moisture and lower rate of diffusion contributes to reduce the rate and extent of ASR expansion (reported in a separate paper). (C) 2013 Elsevier Ltd. All rights reserved.