The presence of piroxicam in breast milk was determined by HPTLC during initial and long term dosing in 4 women treated for arthritis. Piroxicam appeared in breast milk at about 1-3% of the maternal plasma concentration. No accumulation of piroxicam occurred in milk relative to that in plasma up to 52 days of treatment. Neither piroxicam nor its conjugates were detectable in the urine of one breast-fed infant. The daily dose ingested by the infant was calculated to average 3.5% (maximum 6.3%) of the weight-related maternal dose of piroxicam. It is concluded that a breast-fed infant will be exposed to a very small amount of piroxicam.