Publisher Summary This chapter highlights various analytical procedures and chemical analyses presented in the publication Petrology of the Ocean Floor, Volume 33. Most of the chemical analyses presented in the book were performed at the Centre Océanologique de Bretagne. Both electron scanning microscopy and point analyses were performed with the help of M. Bohn on a computerized electron microprobe unit (Camebax). The electron beam incidence of the Camebax has a take-off angle of about 42° and the limit of detection is about 1000 parts per millions (ppm). The precision of the method used is about one percent of the absolute value of concentration. X-ray fluorescence analyses of bulk-rock samples were performed at the Centre Océanologique de Bretagne by H. Bougault, P. Cambon and J. Etoubleau using a Siemens instrument. The powdered samples are fused with lithium tetraborate containing lanthanum oxide that forms a glass disc. Both major and minor elements are analyzed. The chapter also discusses alteration of basaltic rocks, crystallization index, and differentiation index.