Purpose To quantify the level of normal bulbar conjunctival hyperaemia using the Cornea and Contact Lens Research Unit (CCLRU) grading scale, and to investigate inter-observer agreement. Methods Bulbar conjunctival hyperaemia was assessed by two trained observers, using the CCLRU grading scale (zero to four units) interpolated into 0.1 increments, on the right eye of 121 healthy, non-contact lens-wearing subjects (male ¼ 58, female ¼ 63, median age ¼ 28 years, range 16-77). The eye was observed using a slit-lamp bio-microscope ( Â 10 magnification) under diffuse, white illumination. The subject's position of gaze was directed to allow grading of four quadrants: superior, nasal, inferior, and temporal conjunctiva. Bulbar redness was defined as the average of those four grades of conjunctival hyperaemia. A further twenty subjects were recruited to assess interobserver agreement (male ¼ 8, female ¼ 12, median age ¼ 23 years). Results The average bulbar redness was 1.93 (70.32 SD) units. The nasal (2.370.4) and temporal (2.170.4) quadrants were significantly redder than the superior (1.670.4) and inferior (1.770.4) quadrants (Po0.0001). Males had redder eyes than females by 0.2 units. Inter-observer 95% limits of agreement for bulbar redness was 0.38 units. Conclusions The average bulbar redness of 1.9 units was higher than expected, reflecting the design of the grading scale. A bulbar redness of greater than 2.6 units may be considered abnormal, and a change in bulbar redness of Z0.4 units may be significant.