Choroidal melanoma is a rare cancer but the most common intraocular tumor in adults; management of these tumors has been controversial due to the small number of affected individuals, and lack of standardized treatment and follow-up. Currently, prospective randomized clinical trials are being conducted to investigate effectiveness of treatment for medium and large choroidal melanoma. However, small choroidal melanoma sometimes present diagnostic difficulties and there is not consensus regarding their management. Observation has been the preferred method of management for these melanoma until tumor growth has been demonstrated even through little is known about the growth characteristics and natural history of small choroidal melanoma. Previous investigations have identified various histopathologic and clinical predictors of survival but these have been based mainly on retrospective series of cases managed by enucleation. The purpose of the proposed research is to analyze an existing data set collected as part of a prospective observational study of small choroidal melanoma conducted from January 1987 through August 1989 by clinical centers participating in the Collaborative Ocular Melanoma Study (COMS). Small choroidal melanoma were defined as tumors measuring between 1 mm and 3 mm in apical height and 5 mm to 16 mm in basal diameter. Patients with small tumors were managed according to patient and physician preference and followed up to 2 years. Ophthalmic and medical history data were collected at baseline and annually until closure of the study to patient enrollment in 1989. A detailed description of the baseline pathologic features of these tumors was coded from color photographs and fluorescein angiograms. In addition, information from a physical and systemic evaluation of the patient was collected at baseline and prior to administration of any management other than observation. The aims of the proposed analyses are: 1) to provide a description of the baseline ophthalmic and photographically apparent characteristics of small choroidal melanoma, 2) to document rate of growth of small tumors, and 3) to determine clinical and photographically documented predictors of growth for small choroidal melanoma. These analyses will provide a valuable description of the short-term natural history of small tumors and may suggest guidelines for the design of a future randomized clinical trial of treatment for small choroidal melanoma by identifying those at highest risk of short-term growth. Growth is believed to be predictive of both metastasis and death.