A case of right unilateral exophthalmos secondary to metastatic carcinoma of the prostate, in a 68 years old negro patient in which the ocular manifestation lasted 9 months is reported The extrinsic movements of the eye were limited. Pupils reacted slightly to light and accommodation. There was no ocular convergence. The vision of the right eye was blurred and there was mild color vision. The prostate was found to be petrous by touch specially in the right portion. The laboratory findings pointed to a prostatic carcinoma. Bone X-rays were strongly suggestive of metastatic tumour. The histological examination of the orbital tumour showed prostatic tumour cells.