43 cases (86 eyes) of primary chronic angle-closure glaucoma (PCACG) and 44 cases (77 eyes) of primary acute angle-closure glaucoma (PAACG) randomly selected, and 30 normal subjects (34 eyes) were performed ultrasonic biometry of anterior chamber depth, lens thickness and axial length of the globe. By a micrometer attached to the slip-lamp, the width of the anterior chamber angle entrance was also calculated. The clinical manifestations and the natural course of PCACG, including the morphology of the anterior chamber angle and the peripheral anterior synechiae (PAS) as well as the dynamic changes in aqueous outflow were investigated. It was found that there were significant differences in the biometric parameters of the anterior segment between PCACG and PAACG or normal eyes. Follow-up study of the early stage PCACG cases showed that topical miotics and/or peripheral iridectomy effectively prevented the formation of PAS and the progressive development of PCACG. The criteria for diagnosis and the principles for treatment of PCACG were stipulated. The pathogenesis of PCACG was discussed, and it was emphasized that minor attacks of PAACG and its progressive stage should not be confused with PCACG.