Adsorbed oxygen increases both the response and the response time for the photovoltaic effect in rutile.The model for the effect of chemisorbed oxygen on the photoconductivity has been modified to take into consideration the effect of oxygen pressure. The conductance of rutile, measured as a function of oxygen pressure, agrees with the modified model.The increase in photovoltaic response and response time with exposure to oxygen has been explained in terms of the barrier layer formed by chemisorbed oxygen.