The mass spectrometric fragmentation of adamantane, adamantane-d6, diamantane, 1- and 2-adamantanol, and 3,5,7-trimethyl-1-adamantanol has been re-examined, and new data for diamantane and 3,5,7-trimethyl-1-adamantanol are presented in more detail. Metastable peak data have been used to support potential fragmentation pathways. Simple statistical considerations applied to peak intensity data seem to indicate that ionization occurs at the primary bridgehead in both adamantane and diamantane, and that loss of a primary hydrogen is favored over loss of a secondary hydrogen atom.