Animal behaviourists, in general, and those of the ethological persuasion in particular, carry out many field studies on the behaviour of animals in their natural environments. Field experiments include those in which animals, living in their usual surroundings, are subjected to manipulations such as the introduction' of dummies (models), the supplementation or reduction of their food supply, the playing-back of recorded animal sounds, their capture, alteration of appearance and release and the application of telemetric recording equipment. Such studies have an important part to play in our understanding of behavioural ecology. These techniques, of course, interfere with the animals to varying degrees and there may, at times, be ethical problems involved in their use. Is suffering being caused? Is there likely to be loss of life? Is it possible that the environment may be damaged? A paper which looks critically at the techniques used in field research and assesses some of the ethical issues has recently been published in the journal Animal Behaviour. The point is made that it may be possible to accept some level of distress in animal experimentation if the purpose is the alleviation of human suffering, but it may not be acceptable if the goal is the satisfaction of intellectual curiosity alone.