In 1972, chemical analysis of rocks using a dispersive X-ray fluorescence system was shown to be practicable at sea during the "Gibraco cruise" of the R.V. Jean Charcot (Bougault and Cambon, 1973). The same equipment and techniques were used to perform analyses on Glomar Challenger during Leg 37. The aim of this report is to describe the instruments used, the basic routine operations, the problems encountered, and how they were solved. From the experience of analytical work onboard and the precision of the results which is discussed, some brief recommendations are made to IPOD for shipboard chemical analysis. The preliminary results obtained are discussed in terms of chemical units compared to lithological units defined onboard. [NOT CONTROLLED OCR]