This paper describes microanalysis techniques using secondary ion mass spectrometry (SIMS) to measure the abundances and isotopic compositions of hydrogen, carbon, fluorine, sulfur and chlorine in volcanic glasses. SIMS measurement of total H2O and total CO2 abundances compare very well with measurements on the same glasses using vibrational spectroscopy techniques (FTIR). A typical 10-min SIMS measurement for volatile abundances is made on a singly polished specimen, sputtering a crater 15–30 μm in diameter and 2–3 μm deep, utilizing 1–5×10−9 g of sample material. Detection limits are routinely