Circulating immune complexes (CIC) were estimated in 31 cases of head and neck malignancies by polyethylene glycol (PEG) precipitation and latex agglutination inhibition (LAI) techniques. Results were compared with 25 age and sex-matched control volunteers. Seropositivity for CIC by PEG precipitation test was 54.83% compared to 61.29% by LAI test. No positive case was detected in control group. Seropositivity for CIC by combination of both test results was 67.74%. In stage I cancer seropositivity for CIC by both techniques was 33.33%. In stage II it was 36.36% by PEG precipitation test and 45.45% by LAI test. In stage III it was 64.28% by PEG precipitation test and 71.42% by LAI test. In stage IV all cases were seropositive by both techniques. LAI test was more sensitive in CIC detection in cancer stages II and III. PEG precipitation test had the advantage of detecting quantitative CIC levels by PEG index. Follow-up in 10 postoperative cases revealed significant decline in CIC levels by both tests (p < 0.01) after 3 months of surgery; 90% patients became seronegative for CIC by PEG precipitation technique while 80% became seronegative by LAI technique. However, 15 patients were followed up after 3 1/2 years of surgery; 75% patients remained seronegative while 25% patients became seropositive by both tests and manifested clinical recurrences.