There are two components involved in evaluating age by luminescence. One is the equivalent dose determined from luminescence measurements on mineral crystals (usually quartz or feldspar) extracted from the material to be dated. The other is the dose rate to which the crystals have been exposed throughout antiquity. The age is then the ratio (equivalent dose)/(dose rate). Factors which influence the accuracy of the two components, and so the accuracy of the age, are discussed. Limiting factors are identified in order to recognize aspects of measurement on which future development must concentrate to achieve an improvement in accuracy of age determination.