Bioavailability of ketoprofen associated with aluminum phosphate was studied. Subjects were studied after an initial dose given without gastric protection, after ingestion of a single dose given with aluminum phosphate and, lastly, after four days of continuous treatment with this product. Results of plasma peak level and its time of occurrence, area under the curve, half-life and elimination constant establish that bioavailability of ketoprofen is not changed by association with aluminum phosphate. It is therefore unnecessary to modify dosages in such combination treatment. Lastly, there is no change in ketoprofen absorption liable to alter its efficacy.