The isolation of tubules and cells from human kidney cortex was realized by an enzymatic method. Tubules and cells were released from slices of kidney cortex by collagenase. The yield amounted to 80 % of the wet weight of incubated cortex slices. Thus numerous experiments with isolated tubules from one organ could be performed. Glucose production from different substrates was measured in order to test the biochemical integrity of the isolated cells. The highest rates of glucose formation were obtained with fructose as precursor. Glucose production was higher from lactate than from pyruvate. With proline and glutamine as substrates only small amounts of glucose were produced. Glucose formation from 10 mmol/1 pyruvate was linear with time up to 80 minutes. Ado-3':5'-P stimulated glucose formation at 10 mumolar concentration and inhibited gluconeogenesis at 1 mmolar, 0.1 mmolar and 1 mumolar concentrations.