A Thesis submitted to the Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy / Pterygium, a wing-shaped fibrovascular growth of the conjunctiva onto the cornea, can impair vision and be cosmetically unacceptable. Its frequency varies in Africa and postsurgical recurrence in blacks may be high. Determinants of pterygium occurrence and recurrence in rural Africans are not known. This study aimed to establish the determinants of pterygium occurrence and recurrence in rural blacks. The case controlled study comprised 230 patients and 157 controls. Interviews and eye examination were conducted; however, data from 150 patients and 150 controls were analyzed as pre-calculated. Families of 51 cases and 50 controls were studied. Surgery was done on 200 eligible patients. Those who experienced post-surgical recurrence were subclassified as cases and those who did not, controls. Immunohistochemistry was done on 59 pterygium sections and 7 controls. Family history of pterygium was present in 46 cases (30.6%) of 150, and 15 controls (10%) of 150; Odds ratio (OR) =3.93; p <0.01. Traditional eye medication was used by 79 cases (52.6%) of 150, and 60 controls (40%) of 150; OR =2.03; p <0.01. The tear film was unstable in 10 cases (6.6%) of 150, and 26 controls (17.3%) of 150; OR =0.30; p <0.01. Groups of 3-5 individuals per household were pterygium-affected in 36 pterygium families (70.5%) of 51 vs. 1 control (2%) of 50. After surgery, only 190 patients completed followup for a minimum duration of 6 months, and 52 (27.4%) experienced post-surgical recurrence. Of the 52 cases, 21 (40%) had grade 2 pterygia v. 8 post-surgical controls having grade 2 pterygia (6%) of 138; OR =9.1; p <0.01. The limbal basal epithelium expressed p53 in 11 pterygia (18.6%) of 59 v. 5 controls (71.4%) of 7; p <0.01. It expressed matrixmetalloproteinase-1 (MMP1) in 14 pterygia (23.7%) of 59 v. 5 controls (71.4%) of 7; p =0.02. MMP2 and MMP3 were detected in 16 cases (27.1%) of 59 v. 5 controls (71.4%) of 7; p =0.03. Pterygium occurred in families and was associated with traditional eye medication. Pterygium occurrence was not associated with unstable tear film, p53, and MMPs. Postsurgical recurrence was connected to grade 2 pterygia.