This paper is concerned with the extent to which rehabilitation tax credits affect the conditional probability of commercial real estate rehabilitation. The analysis suggests that rehabilitation tax credits have been a significant determinant of the conditional probability of rehabilitation in the Boston office market. A significant portion of rehabilitation tax credit investment is investment that would have been invested elsewhere, about 60% to 65% in certain periods, but rising to as high as 90% in other periods. The findings indicate that the rehabilitation tax credit has a significant and substantial influence on the conditional probability of rehabilitation. The findings also reveal that the greatest amount of slippage, not too surprisingly, generally occurs when the tax credit is low and when the gain from rehabilitation before the tax credit is high.