Aim: To identify patients with visceral heterotaxy who are at risk from fulminant sepsis. Methods: We studied 38 patients, 37 having undergone abdominal ultrasound, all 38 having examination of blood films to establish presence of Howell-Jolly bodies, and all 38 documented to have had pneumococcal vaccination and prophylaxis with penicillin. We checked whether the parents were aware of the splenic state of their child, and when possible, we compared current results of blood films with those obtained postnatally. Results: Two of the 17 patients with multiple spleens, all 11 without a detectable spleen, and 1 of 9 patients with a normal spleen, showed Howell-Jolly bodies in their blood films. In 5 of 23 patients with serial blood films, Howell-Jolly bodies had not been seen postnatally, but could now be detected in current blood films. Of these patients, 2 had multiple spleens, 1 did not have a spleen, and 1 had a solitary spleen of normal size. In the other patient, ultrasound could not be performed. Only one of these patients was receiving penicillin prophylactically, and had received pneumococcal vaccination. Of the 15 patients in whom Howell-Jolly bodies were present in the blood, only 8 parents knew about the potential risk for infection. Another 7 parents were sure that their child was taking penicillin regularly, and had received pneumococcal vaccination. Conclusions: Howell-Jolly bodies can be found in the blood of patients with visceral heterotaxy independent of the anatomical state of the spleen. As Howell-Jolly bodies can be encountered in the blood of such patients with increasing age, those with multiple and solitary spleens should be monitored regularly to identify those at risk. Parental knowledge of the splenic state, and compliance for prophylaxis using penicillin, and pneumococcal vaccination, were unsatisfactory in our cohort.