The paper describes 120 uniaxial tensile failure tests on pultruded glass-fibre-reinforced polymer (GFRP) single-bolt single-lap joints. For each joint, the lap width to bolt/hole diameter ratio (W/D) and bolt diameter (D) were four and 10 mm, respectively. Five end distance to bolt/hole diameter ratios (E/D) and four test temperatures were investigated. The joints were sub-divided into 20 groups – one for each E/D and temperature combination – and each group comprised six nominally identical joints. In addition to the joint tests, a number of uniaxial tensile failure tests were carried out on the virgin GFRP plate of the joints' laps. Mean ultimate loads and extensions derived from the joint failure tests were used to compile graphs of ultimate stress and overall failure strain as functions of joint geometry and test temperature, from which corresponding characteristic values were obtained. In addition, knock-down factors, which express the ultimate stresses of the joints, relative to the ultimate stress of the virgin GFRP plate, were derived. The knock-down factors were compared with those obtained earlier for single-bolt double-lap joints. The factors may be useful for the preliminary design of single-bolt tension joints.