Previous reports have described the presence of apoproteins A in subretinal fluid (SRF). We studied the presence of total apoprotein A (apo A) and apoprotein A-I (apo A-I), using the method described by Laurel in SRF and its levels in serum in 20 patients with retinal detachment. By this method we can quantify the concentrations of apoproteins in SRF. All cases showed the presence of these apoproteins in SRF. The mean +/- standard deviation obtained was 78.7 +/- 26.94 mg/dl and 173.35 +/- 30.08 mg/dl for total apo A in SRF and serum respectively. For apo A-I these values were 32.62 +/- 14.36 mg/dl in SRF and 123.4 +/- 24.11 mg/dl in serum. We found no correlation between levels of total apo A and apo A-I in SRF and its levels in serum. Statistical differences were found between apo A-I content in SRF from detachments with the size of 3 quadrants and that of 1 and 2 quadrants but not between 3 and 4 quadrants. When the detachment affected 1 and 2 quadrants the concentrations of apo A-I were statistically lower. No statistical differences were found between concentrations of total apo A and apo A-I in SRF and the duration or presence of PVR in the detachments. These findings suggest that the outer blood retinal barrier is preserved during rhegmatogenous retinal detachment.