There exist no recommendations as to how aggregate research ă results should best be disclosed to long-term cohort participants. ă Objective To study the impact of cohort results disclosure documents of ă various kinds on participants' satisfaction. ă Design Randomized study with a 2x2 factorial design. ă Setting and participants The GENEPSO-PS cohort is used to study the ă psychosocial characteristics and preventive behaviour of both BRCA1/2 ă carriers and non-carriers; 235 participants wishing to receive ă `information about the survey results' answered a self-administered ă questionnaire. ă Interventions The impact of providing the following items in addition to ă a leaflet about aggregate psychosocial research results was investigated ă (i) an up-to-date medical information sheet about BRCA1/2 genetic ă topics, (ii) a photograph with the names of the researchers. ă Main outcome measures Satisfaction profiles drawn up using cluster ă analysis methods. ă Results Providing additional medical and/or research team information ă had no significant effect on satisfaction. The patients attributed to ă the `poorly satisfied' group (n = 60, 25.5%) differed significantly ă from those in the `highly satisfied' group (n = 51, 21.7%): they were ă younger [odds ratio (OR) = 0.96, 95% confidence interval (0.92-0.99), ă P = 0.028], less often had a daughter [OR = 4.87 (1.80-13.20), P = ă 0.002], had reached a higher educational level [OR = 2.94 (1.24-6.95), ă P = 0.014] and more frequently carried a BRCA1/2 mutation [OR = 2.73 ă (1.20-6.23), P = 0.017]. ă Conclusions This original approach to disclosing research results to ă cohort participants was welcomed by most of the participants, but less ă by the more educated and by BRCA1/2 carriers. Although an easily ă understandable document is necessary, it might also be worth providing ă some participants with more in-depth information.