OBJECTIVE: To analyze the expression of molecules involved in cell proliferation and apoptosis in primary and recurrent pterygium tissues and to test the relationship between cell proliferation/apoptosis and neovascularization in pterygia. STUDY DESIGN: Forty-two primary pterygium tissues and 35 recurrent pterygium tissues were collected from January 2012-December 2015 for this single-center study. The tissues were analyzed by immunohistochemistry with anti-PCNA, Ki-67, Bax, Bcl-2, mutant p53, survivin, and VEGF antibodies. The anti-CD31 antibody was used to stain the microvessels in pterygia. RESULTS: The rate of positive PCNA and Ki-67 expression was significantly higher in the recurrent pterygium samples than in the primary pterygium samples. Molecules associated with apoptosis did not differ between the primary and recurrent pterygium samples. The formation of microvessels was more pronounced in the recurrent pterygium samples than in the primary pterygium samples. Microvessel density showed a correlation with the number of Ki-67-positive cells. The recurrent pterygia of younger patients (age < 65) showed a significantly higher number of Ki-67-positive cells (p=0.01). OBJECTIVE: To analyze the expression of molecules involved in cell proliferation and apoptosis in primary and recurrent pterygium tissues and to test the relationship between cell proliferation/apoptosis and neovascularization in pterygia. STUDY DESIGN: Forty-two primary pterygium tissues and 35 recurrent pterygium tissues were collected from January 2012-December 2015 for this single-center study. The tissues were analyzed by immunohistochemistry with anti-PCNA, Ki-67, Bax, Bcl-2, mutant p53, survivin, and VEGF antibodies. The anti-CD31 antibody was used to stain the microvessels in pterygia. RESULTS: The rate of positive PCNA and Ki-67 expression was significantly higher in the recurrent pterygium samples than in the primary pterygium samples. Molecules associated with apoptosis did not differ between the primary and recurrent pterygium samples. The formation of microvessels was more pronounced in the recurrent pterygium samples than in the primary pterygium samples. Microvessel density showed a correlation with the number of Ki-67-positive cells. The recurrent pterygia of younger patients (age < 65) showed a significantly higher number of Ki-67-positive cells (p=0.01). CONCLUSION: Higher levels of cell proliferation were detected in recurrent pterygia than in primary pterygia. Microvessel density was correlated with cell proliferation. Recurrent pterygia showed higher rates of cell proliferation in younger than in older patients in this single-center study. © Science Printers and Publishers, Inc.