[EXPR: a simple computer system for recording animal behavior].

A number of different methods for recording animal behaviour are briefly reviewed and the computer system "EXPR" for the ethological recording of the sequences of behavioural events is described in this article. The main peculiarities of the system are: (a) recorded data are saved to the files created by a data analysis package, (b) it is possible to record simultaneously behaviour of a number of individuals, which is crucial for the analysis of social interactions. The user can specify the options for different recording tasks through the setup file written with using special notation. The program functioning is illustrated by an artificial example.