Anecdotal reports have described association of cyclic edema with sensitivity to specific foods. Although it occurs in children, this study was carried out in 4 women, ages 23-48 yr. Fasting 4 days on distilled water resulted in wt loss (avg 3.9Kg) and elimination of edema. Individual food challenges, 4 daily, were then performed for 10 days. Measurements of wt. and urine output were obtained on constant fluid intake. Urine volumes were collected 4 hr after ingestion of foods and for each 24 hr period. Serum and urine osmolality, electrolytes and aldosterone and serum cortisol, C3, and immunoglobulins G, A, M, and E were measured serially. The decreased wt and loss of edema were maintained throughout the study period except for transient fluid retention after ingestion of particular foods. Specific foods caused decrease in 4 hr urine output to amounts less than 1 S.D. from mean 4 hr urine volume. Fifteen foods were found to produce fluid retention. Reactions were reproducible. Four patients had high serum IgE and 3 and 4 elevated IgM levels. During positive tests, urine output decreased within one hr unassociated with increased urine osmolality. A direct vascular effect with decreased renal blood flow is a likely explanation. Elimination of test positive foods resulted in good control of edema in all patients.