Purpose: AG3340 (prinomastat) is a nonpeptidic, small-molecular-weight, synthetic matrix metalloproteinase inhibitor (MMPI) with selective inhibitory action of MMP-2, MMP-9, MMP-3, and MT-MMP1. We evaluated AG3340 injected intravitreally to treat choroidal neovascularization in a laser induced rat CNV model. Methods: In the pretreatment group, the drug was injected the same day after induction of choroidal neovascularization by diode laser. In the treatment group, the drug was injected 2 weeks after induction of choroidal neovascularization (CNV). Fluorescein and indocyanine green angiography were performed to evaluate CNV. ERG recordings and histology were performed to assess toxicity and the CNV lesions. Results: When used at the time of CNV induction, 62.8% of lesions in control versus 22.8% of the laser lesions in treated eyes developed CNV (p < 0.0001). The invading fibrovascular complex was thicker in the control eyes than that in the treated eyes. No signs of toxicity were detected. When used to treat established CNV, the percentage of leakage in treated and control eyes were 54.1% and 58.9% respectively (p > 0.05). Prinomastat was effective when given at the time of induction of CNV in the rat model. Administration of prinomastat 2 weeks after laser induction did not show efficacy. Conclusion: Prinomastat was active in the earliest stages of experimental CNV. It might be best used in combination with photodynamic therapy to inhibit recurrence of CNV from temporarily closed new vessels.