This paper outlines the results of a study into the effect of rock specimen size on the anchorage performance of a hollow strand bulbed cable bolt. As part of the design of a Laboratory Short Encapsulation Pull Test (LSEPT) facility, a question arose as to the appropriate size of the rock sample in which the cable bolt is embedded and whether size might affect the pull out strength of the cable bolt. An analysis of previous research revealed little information regarding the rationale for the sample size used in previous test work. Many of pull out tests in the past had made use of either a rigid encasment such as steel, aluminium, or PVC casing or a biaxial pressure cell to apply a constant stress to model the in situ rock mass conditions. A test arrangement was developed to assess whether there was any appreciable change in anchorage performance with varying diameter of the rock sample. Cable bolts were embedded into the rock sample using a polyester resin grout having diameters of 150 mm, 215 mm, 300 mm and 450 mm with a constant embedment length of 280 mm. A hollow hydraulic ram was used to load the cable bolts to failure. The results indicate there was a size effect albeit only marginal whereby an increase in the diameter resulted in increased anchorage capacity of the cable bolt.