A brief description of manganese nodule morphology and mineralogy is given, and detailed information on 74 elements in Pacific manganese nodules is presented. For the major elements and some minor and trace elements, the data are divided into four areas of the Pacific: the Clarion-Clipperton fracture zone region, the mid-Pacific seamount region, other abyssal plain region (>3,000 m depth), and other seamount, ridge, and continental margin region (<3,000 m depth). For all 74 elements, data tables are presented, and for 21 elements, the data are broken down by area. Where only limited data are available for certain elements, the data are presented as a composite of the entire Pacific ocean. The possible chemical form, mineral-element associations, and interelement correlations are given.