The pooling of five individual serum samples for the detection of human immunodeficiency virus type 1 (HIV-1) antibodies was examined to assess whether testing pooled versus individual sera was technically feasible. Detection of HIV-1 antibodies was performed using a competitive enzyme immunoassay (EIA) Wellcozyme HIV Recombinant commercially available kit. Positive, weak positive and negative sera or HIV-1 antibody from Wellcozyme HIV Recombinant, Du Pont ELISA, SERODIA HIV Mast Diagnostica and from "Stefan S. Nicolau" Institute of Virology (NIV) collection were pooled in various dilutions with control negative sera for HIV-1 antibodies. When positive sera were pooled 1:4 with negative sera, results remained reactive in the same range of positivity and when cut off-control sera were pooled 1:4 with negative sera samples remained in the cut off range. For reliability we considered cut of values of pooled sera probes an A 450 absorbance 0.2 units higher than the absorbance of cut-off-control from Wellcozyme HIV Recombinant kit B. Samples of pooled sera that have absorbance A 450 lower, equal or 0.2 units higher than the absorbance of cut off-control of Wellcozyme were considered positive and the five sera were tested as individual probes. The positive probes thus found were retested in duplicate using the original sample source. Negative samples of pooled sera do not have to be retested, this being the main advantage of this technique. Also positive sera (controls of from NIV collection) were pooled with HIV-1 antibody negative sera which were positive for rheumatoid factor (RF).(ABSTRACT TRUNCATED AT 250 WORDS)