Biodegradation of cellulose acetate and a cigarette filter is being evaluated under variable conditions. In a compost based on ISO14855 (58 ± 2 °C), 60% decomposition was reached within 40 days. There was no considerable difference between the decomposition rates of a filter tip and acetate flakes. The fact that a filter tip as is and powdery flakes which can mix more evenly with compost showed similar decomposition rates implies a rate determining factor scarcely affected by the form of samples. It is in good accord with recent reports suggesting the trigger on biodegradation by the hydrolysis of ester bonding of cellulose acetate at the high temperature and humidity. Another noticeable result is a filter tip lost 60% of its weight at 80 days in an anaerobic sludge even at 30 °C. This anaerobic decomposition seems to be a totally biological process. These results showed that cellulose diacetate and a cigarette filter made of it is intrinsically biodegradable under various conditions.