Anxiety associated with blood and injections is a common problem in medical settings and, in severe cases, affects sufferers' ability to receive medically essential treatment. The present study was conducted to examine incidence of adverse reactions to venipunctures among phlebotomy patients, as well as to understand the demographic and psychological characteristics associated with such reactions. A large sample of participants undergoing venipuncture (N=3315) was recruited from hospital-based phlebotomy laboratories. Participants completed a brief questionnaire assessing psychological and physiological reactions to having their blood drawn. Results indicated that a small minority of patients experienced significant anxiety symptoms during venipuncture. Vasovagal reactions and vasovagal syncope were extremely infrequent. A tendency to experience pain, disgust, and fear of fainting during injections was associated with anxious responding to the venipuncture and a probable diagnosis of needle phobia. Theoretical and practical implications are discussed.