This study was designed to improve the understanding of the mechanisms that govern the origin of retinal detachment (RD) by examining the quantitative composition of proteins in the subretinal fluid (SRF). Inflammation proteins and immunoglobulins (Ig) were titrated from SRF and sera in 25 patients with RD The following concentrations were found in SRF: total proteins 16 g/l, albumin 12.6 g/l; pre-albumin 0.37 g/l; transferin 1.8 g/l in 68% of cases; haptoglobin and alpha 2 macroglobin were present in only one SRF: alpha 1 antitrypsin 0.86 g/l in 48%; orosomucoid 0.57 g/l in 32%; IgG 2 g/l in 52%; IgA 0.17 g/l in 88% and IgM 15.9 mg/l in 56%. Correlations were found between the duration of detachment and the concentration of total proteins (p < 0.01). The extent of RD was correlated with the concentration of IgG or IgA in the SRF (p < 0.01). These findings suggest that the correlation between the Ig concentration and the extent of RD is an argument for the participation of choriocapillaris in the genesis of SRF.