1. 1. Amphiuma means kidney fragments were cultured for up to 6 weeks in three different media (Leibovitz L15 (L15), Minimum Essential Medium (MEM), MEM + urea). 2. 2. Ammonia was released into the culture medium for up to 5 weeks; the amount produced was greater in L15 medium, which has a higher amino acid content than MEM. 3. 3. Kidney fragments contained glycogen after 5 weeks in culture in all three media. 4. 4. There was an increase in mitotic incidence in culture, which was significantly greater in one animal in medium with added urea. 5. 5. The relationship between function and proliferation in the kidney is discussed.