Two selected cases of retinal vasculitis, apparently of unknown aetiology, are reported; one case without any systemic or laboratory manifestation and the second case with a clinical picture similar to VKH syndrome and immunodepression. Both cases showed abnormal haematological parameters related to blood viscosity in the early and acute phases which could be manipulated by therapy. Reduction or near normalisation of these haemorrheological parameters coincided with clinical and angiographic improvement. The second case with severe immunodepression was found to be retrovirus HIV-2 positive.