Abstract: A rapid, safe and efficient process for the digestion and destruction of organic matter in materials of biological origin. Acid mixtures (nitric and perchloric acids for ashing; appropriate acid mixtures for other digestions) are added to the sample and then heated internally by absorption of microwave energy from a precisely controlled field within a specially modified microwave oven.Apparatus used for the digestions include a microwave oven equipped with an internal, acid-fume resistant box or liner, a positive flow ventilation system through the box, and an acid-fume trap or scrubber for treating the exhaust fumes from the box. Additional apparatus includes a precise timing system for controlling the delivery of microwave energy, or an interrupted duty cycle timing system.