Summary:Immunological status may predict clinical outcome in BCG treated melanoma. P. M. Reynolds. G. Grimsley. R. L. Dawkins, M. J. Byrne and P. J. Zilko.Aust. N.Z. J. Med., 1980,10, pp. 39–43.Twenty‐seven patients with surgically reseated stage Il or III malignant melanoma were treated with bacillus Calmette‐Guérin (BCG) and followed prospectively to determine whether relapse could be predicted. Peripheral blood mononuclear (lymphocyte plus monocyte) counts (PBM), T and B cell counts, phyto‐haemagglutinin (PHA) cytotoxicity, PHA transformation, antibody‐dependent cell‐mediated cytotoxicity (ADCC) and serum immunoglobulin concentrations were studied before and during therapy. Patients ultimately classified as having a poor clinical outcome (inoperable recurrence) were compared with those with a more favourable outcome. Prior to therapy, poor outcome patients had lower PBM and T cell counts but there was some overlap. After three months, these differences were more pronounced. Low PHA cytotoxicity was also associated with poor outcome; again the differences were more apparent at 3 months than prior to therapy.These results suggest that PBM, T cell counts and PHA cytotoxicity may predict poor outcome some months before inoperable recurrence is appare