In this paper, an experimental investigation on the effect of silica fume and size of aggregate on the long-term drying shrinkage of mortar is reported. Silica fume was used as a partial replacement by weight of cement from 0% to 30%. The maximum size of fine aggregate was 1.18 and 2.36 mm, respectively, in series I and II mortar mixes. The water-cementitious material ratio and the cementitious material-sand ratio were 0.50 and 1:3. The ultimate drying shrinkage was measured up to the age of 1095 days. From the experimental test results, it was observed that the addition of silica fume has a significant influence on the drying shrinkage at early ages of mortar. It increases with increase in silica fume content. This increase in early days drying shrinkage is due mainly to very high pozzolanic reaction and pore size refinement mechanism of silica fume. The drying shrinkage in mortars with higher contents of silica fume was observed to be as high as 7-10 times greater than that observed in mortars without silica fume at early days. No significant influence of silica fume was found on the long-term drying shrinkage of mortar. Furthermore, it has been dramatically observed that the long-term drying shrinkage of mortar decreases with the increase in the size of fine aggregate. © 2001 Elsevier Science Ltd. All rights reserved.