Purpose: Acrylic resin complete dentures exhibit dimensional changes mainly because of processing shrinkage and expansion because of water uptake. The aim of this 5-year clinical study was to determine the dimensional changes occurring during construction and in service in maxillary complete dentures made of two types of acrylic resin. Materials and Methods: Complete dentures were constructed for 17 edentulous patients. Nine patients received dentures made of conventional heat-cured acrylic resin, and eight patients received dentures made of rapid heat-cured acrylic resin. Measurements were taken across three reference points (second molars bilaterally and central incisors) on six occasions: at the flasking stage, at the denture insertion appointment, and after 1 week, 1 month, 3 months, and 5 years of use. The data obtained were analyzed using one-factor repeated-measures ANOVA, one-way ANOVA, and Duncan’s multiple comparisons test. Results: The two types of dentures showed the same pattern of dimensional changes. A shrinkage of up to 0.27% was estimated at the insertion stage. During the first 3 months of use, a decrease of the initial dimensional change was observed. After a 3-month period, a gradual compensation for the initial shrinkage started to take place. At the end of the study period (5 years), an expansion of up to 0.35% was measured. Conclusion: Maxillary complete dentures made of either conventional or rapid heat-cured acrylic resin exhibited dimensional changes that were considered clinically acceptable. Int J Prosthodont 2003;16:78–81.