When loads are applied to a masonry structure, viscoelastic behaviour is exhibited where the response can be divided into two distinct parts: an instantaneous elastic part and a time-dependent part. With the change in masonry construction during the last century, the latter portion of the response is becoming more important in the design of masonry structures. The effects of mortar type, stress level, age at loading, moisture condition, and masonry strength on the creep behaviour of clay masonry structures are examined. The results of a continuing experimental programme, begun in 1988, were used to evaluate the variations in specific creep of clay masonry with the different parameters considered. The test setup and the effect of moisture content on the creep behaviour of clay masonry are also described briefly.Key words: masonry, creep, specific creep, creep ratio, mortar type, moisture condition.