This study examined participation rates and reasons for refusal in a genetic study of human epilepsy. The study enrolled children with epilepsy and their parents, and required signing informed consent, verbalizing assent, and giving a peripheral blood sample. One hundred sixty-eight children met inclusion criteria; 137 agreed to enroll (82%), and 31 refused (18%). Sixteen of thirty-one patients (52%) who refused cited fear of phlebotomy as the reason for refusal. All patients refusing due to fear of phlebotomy did not require blood tests for clinical purposes. As fear of phlebotomy is the primary reason for study refusal, obtaining DNA samples from a buccal swab or mouthwash protocol may be an alternative for some studies, although there are limitations to these methods. Further analysis of the factors influencing decisions to decline study enrollment is warranted. These data will help in the design of future genetic studies and may increase future participation rates.