Aim: The study was conductedto determine the pattern of diurnal change of intraocular pressure in glaucoma suspects and controls attending National Eye Centre, Kaduna. Methods: It was a hospital based comparative study comprising two groups; Glaucoma suspects and normal controls. Diurnal variation of intraocular pressure was measured in 213 eyes of 107 Glaucoma suspects (defined as the presence of any one of: vertical cup disc ratio of > 0.5 in one or both eyes with normal IOP and visual fields; or IOP of > 21mmHg in one or both eyes on at least two occasions with normal optic disc and visual fields or the presence of glaucomatous disc changes with an abnormal visual field suggestive but inconclusive of glaucoma using the Anderson’s criteria) and 204 eyes of 103 normal controls at four hourly intervals for twenty four hours. Results: Overall, the response rate was 100% and 99% for the Glaucoma suspects and Controls respectively. After phasing, the mean IOP peak for both groups was observed between 10-11am and trough between 10-11pm. Based on results of phasing, optic disc findings and visual fields, the glaucoma suspects were re-categorized into four groups (POAG, NTG, Ocular hypertension and Physiologic Cupping). Seventeen percent were not classified due to inconclusive diagnosis.