Approximately one third of patients with chronic hepatitis C virus (HCV) infection have normal alanine transaminase (ALT) levels. We studied the clinical, biochemical, virological, and histological features in patients with persistently normal ALT. A case-control study was conducted on 275 patients with chronic HCV infection, including 75 patients with persistently normal ALT and 200 patients with abnormal ALT. Persistently normal ALT was defined as 4 consecutive ALT values in each patient within a period of 12 months. The average age of the patients was 44 years (range 18 to 69 years). More non-Hispanic whites had persistently normal ALT. The mean serum ferritin level was significantly lower in patients with persistently normal ALT as compared with abnormal ALT (128 +/- 92 ng/mL and 224 +/- 128 ng/mL), respectively (P =.017). The mean HCV-RNA level was significantly lower in patients with persistently normal ALT as compared with abnormal ALT (12 x 10(5) +/- 2.8 x 10(6) copies/mL and 33 x 10(5) +/- 8.0 x 10(6)), respectively (P =.02). Histologically, patients with persistently normal ALT had less severe portal inflammation (P