Over the past 30+ years, he has been on the faculty of three different pediatric departments; the University of Colorado (10 years), the Universidade Federal do Rio Grande do Norte in Natal, Brazil (3 years), and the University of Arizona (30 years).  During his entire tenure at Colorado and Arizona he taught medical students and pediatric residents and had a panel of patients with chronic conditions that he personally followed and was on call for after clinic hours. Most of these patients were special needs children with complicated multi-system problems. He has conducted multiple research projects, most of which developed from individual problems he saw in his patients and where he felt there was not a sufficient readily available answer in the medical literature. He has more than 60 published articles in peer-reviewed medical journals and 20 chapters in medical textbooks. His international experience extends over the past 30 years and has included clinical work, teaching, research, field work, and administrative responsibilities in more than a dozen different countries. He works extensively with the Section on International Child Health with the American Academy of Pediatrics.