Medium-distant clusters of galaxies seen by ISO

We present a comprehensive study of ISO cluster galaxies in connection with other wavelengths. First results show that infrared galaxies detected by ISOCAM concentrate on the edge of clusters. Surprisingly, they are not emission lines galaxies but very luminous elliptical, merging or interacting ones, which suggests non-trivial connections between star formation rate, optical and mid-IR properties. However, no correlation has been found between the MIR/optical star formation properties of the galaxies, so that the exact origin of the IR emission remains unclear.