Background: Recombinant adeno-associated virus (rAAV) is one of the most promising recombinant viral vectors for delivering therapeutic agents to the retina. The present study aims to quantify any effect that an rAAV construct may have on the retina. To be able to use rAAV for therapeutic purposes, the potentially toxic effect of the vector and an associated green fluorescent protein (gfp) marker has to be investigated.Methods: By combining histological analysis with computer scanning techniques, the local toxicity of rAAV and gfp can be measured. This will have obvious implications for its role as a carrier in the rapidly developing world of gene therapy.Results: It is shown that a construct consisting of rAAV and gfp, delivered subretinally to rat eyes, causes no more histological damage than injection with saline alone. Furthermore, via fluorescent fundus photography and computer scanning techniques it is seen that the area exposed to the rAAV−gfp construct is significantly greater than the area of histological change.Conclusions: It is thus concluded that the rAAV−gfp construct has no significant toxic effect, at an anatomical level, on the retina 12 months after injection.