A single-blind, randomized clinical trial of 56 female subjects was conducted to determine whether decreased consumption of caffeine decreases breast pain/tenderness or nodularity in patients with suspected benign proliferative breast disease. The subjects were randomly assigned to one of three groups--a control group (no dietary restrictions), a placebo group (cholesterol-free diet), and an experimental group (caffeine-free diet). At the initial examination, the subjects reported on the presence of breast pain, the degree to which pain affects daily activities, the frequency of pain, the degree of pain associated with breast examinations, and the degree of pain associated with close-fitting clothing. Subjects were then examined and the four quadrants of each breast were rated on a scale of 0 to 3 (0 = normal, fatty tissue, 1 = little seedy bumps or fine nodularity, 2 = discrete nodules or ropy tissue, 3 = confluent areas, hard or soft masses). Subjects in all three groups returned for 2- and 4-month follow-up examinations. Total nodularity scores, degree of pain/tenderness, and compliance with dietary restrictions were analyzed. The data showed that decreased caffeine consumption did not result in a significant reduction of palpable breast nodules or in a lessening of breast pain/tenderness.