The migration of acetaldehyde from polyethylene terephthalate (PET) under various conditions was analysed by headspace gas chromatography and flame ionisation detection. The residual amounts of new PET bottles were about 6.3 mg/kg with a migration value of 200 micrograms/l. On studying the migration at different temperatures and times, behaviour curves characteristic of packing materials made from plastics are obtained. The amount of acetaldehyde diffusing from PET at a temperature of 40 degrees C reached a constant level after 4 days which was about 10% of the residual value of acetaldehyde. On increasing the temperature by 20 degrees C, this level was raised up to 50%. The results of the analysis of acetaldehyde in soft drinks containing carbonic acid show that the migration in fact is not sufficiently high to influence the taste of these soft drinks. A negative effect on the taste may be recognized with mineral waters and soda when they are exposed to higher temperatures (e.g. 40 degrees C or more) over a longer period of time.