We present as simple and efficient algorithm for the approximate median selection problem. The algorithm works in-situ; it is fast and easy to implement. It is also possible to use it "on line," for a stream of data. For a large array it returns, with high probability, a very good estimate of the true median. The running time is linear in the length n of the input: The algorithm performs fewer than $\frac{4}{3}n$ comparisons, and $\frac{1}{3}n$ exchanges on the average.
We show some experimental illustrations of its operation, but most of the talk is about analysis of the quality of the algorithm.