(32)P was applied to a Laminaria digitata thallus and the pattern of (32)P phosphorylated compounds was studied, as a function of time, in the different tissues involved in translocation, i.e. source, pathway and sinks. The results showed that, 3 hours after absorption by the uptake region (lamina), the bulk of the radioactivity was incorporated into organic compounds (70 to 80% of total (32)P taken up), hexose monophosphates being the heaviest labelled. Further change in that region was marked by an accumulation of (32)P in the inorganic pool (65 to 70% after 13 days). Conversely, the (32)P pattern in the medulla of the stipe, which initially showed a similar pattern to the uptake region, did not vary during translocation. The pattern of (32)P distribution into sinks (growing stipe peripheral tissue or hapteron) leads to accumulation of the radioactive element in inorganic and acid-insoluble fractions. These results are discussed in terms of comparative distribution of (32)P in the different parts of the thallus and suggest that phosphate moves as Pi in that alga.