Time‐resolved UV‐visible absorbance measurements made after laser photolysis are important for mechanistic understanding of many biological systems. Some of these systems are available in extremely small quantities and/or are destroyed by light so that averaging strategies for signal‐to‐noise improvement are severely restricted. An apparatus is described which measures the absorbance difference spectrum at a variable delay (10 ns resolution) after photolysis of a 1 &mgr;l sample (optical path 2 mm). After each photolysis pulse the sample is replaced using a pump which delivers 0.5 &mgr;l increments. Waste of sample is avoided by making sure that the sample’s cross section exactly matches the image of the spectrograph slit in the sample cell. Data are presented for photolysis of the bovine visual pigment rhodopsin both in transparent octyglucoside detergent suspensions and more turbid, sonicated disk membrane preparations. Rate constants obtained from a biexponential fit of difference spectra at five delay times from 40 to 640 ns agree well with those obtained previously from much larger detergent samples. Equally high quality results are obtained for the turbid membrane suspensions at longer delay times.