A new sensitive spectrophotometric method based on the reaction of pentachlorophenol (PCP) with concentrated nitric acid to form chloranil that liberates iodine with potassium iodide is described. The liberated iodine bleaches the pinkish red coloured rhodamine-B dye which was measured at 555 nm. Beer's law is obeyed over the concentration range of 1-10 mug of PCP in final solution volume of 25 mL (0.04 - 0.4 ppm). The apparent molar absorptivity and Sandell's sensitivity were found to be 7.34 x 10(5) l mol(-1) cm(-l) and 0.0003 mug cm(-2). The method has been satisfactorily applied to the determination of PCP in air, water, plant material, textile effluent and biological samples.