All patients involved in biomedical research must, according to the Helsinki II declaration, receive complete verbal and written information about the project. Valid consent must be based on adequate information. This study analyses all of the 225 written patient information sheets submitted for approval to the regional research ethical committee covering the three southernmost counties in Jutland (Denmark) during the years 1989 and 1990. Linguistic analysis shows that the information is written in a difficult style with a median readability index of 48.2. It is generally recommended that information directed to the general public should have a readability index below 40 (approximately the level of the popular press). Analysis of information content shows that several important pieces of information are often missing: for instance, information about the name of the leader of the research and about the fact that the relationship with the institution will not be adversely affected by a refusal to participate in the research programme.