Between 1978 and 1988, 307 patients with uveal melanoma were irradiated using helium ions at Lawrence Berkeley Laboratory. The length of follow-up ranged from 1-115 months (median 42 months). The 5-year actuarial treatment results were: local control rate, 96.8%, determinate survival rate, 81%, freedom from distant metastases, 76%, eye retention rate, 83%, and risk of developing neovascular glaucoma, 36%. Long-term vision outcome was analyzed in 81 patients with a minimum follow-up of 5 years. Forty-seven percent of patients retained vision of 20/200 or better. The median change in vision was a loss of four lines on the standard eye chart. Thirty-eight percent of patients had visual acuity either improve or remain within two lines of their pretreatment vision. A multivariate analysis identified tumor size as the only independently significant risk factor affecting survival, development of neovascular glaucoma, or the risk of enucleation; no risk factor correlated with local recurrence. Tumor size, tumor-fovea distance, and pretreatment visual acuity were independently significant risk factors influencing vision outcome. These results confirm that helium ion irradiation is an effective treatment for uveal melanoma which combines high rates of local control, survival, and eye retention with a substantial likelihood of long-term vision preservation.