Luteinizing hormone specifically depletes the pseudopregnant rat ovary of ascorbic acid. This depletion takes place from the corpora lutea as determined by cytochemical methods. The depletion reaction has a characteristic time sequence which resembles that seen in the adrenal gland but takes place over a more prolonged period of time. The onset of depletion is within 15 min of the injection of purified luteinizing hormone, reaches maximum intensity at 3 hr, and ends by 19 hr when a rebound effect is seen. The most striking cytochemical finding is that of "clumping" of ascorbic acid granules, which is first noted at 3 hr and persists until depletion ends at 19 hr. The physiologic significance of this reaction is not well understood.