We examined recruitment to an imaginary trial of hormone replacement therapy (HRT) following two different styles of information about HRT. We predicted that for treatments which, like HRT, are available outside a trial, people offered the facts as currently known would be less likely to remain unsure about the relative costs and benefits, and so less likely to agree to enter a randomised trial. In contrast, when the information provided reflected the current state of uncertainty which justified the trial, we predicted that people would be less likely to form a preference for one treatment arm over the other, and so more likely to agree to enter a trial. One hundred women aged 25-40 years were informed about HRT via a video and an information leaflet. For half the participants the information was framed in a way which emphasised the current state of uncertainty about the relative costs and benefits of HRT, and in that respect it reflected the justification for a trial. This version was considered to be similar in style to information commonly provided to potential trial participants. For half the participants the same information was framed in a way which offered explicit numerical detail about currently known facts, and in that respect it was considered to be similar in style to information commonly available to doctors prior to a trial. Women learned as much about HRT in the two conditions, but women given the explicit versions were more likely (i) to hold a stronger view about whether or not they would take HRT (ratings were not elicited from the first 30 participants in this condition. N = 20, p < 0.05 1 tailed) and (ii) to refuse entry to the trial (N = 50, p < 0.05 2 tailed). Those who, given the explicit version, agreed rather than refused to enter the trial, scored higher on believing that others control their health (p < 0.01 2 tailed).