Objective: To investigate pediatric residents' efforts to assess understanding in discussions about positive newborn screening test results. Newborn screening saves lives, but confusion about false-positive and carrier results often leads to psychosocial problems. Design: Explicit-criteria abstraction of transcripts of encounters with standardized parents of a fictitious infant found to carry cystic fibrosis or sickle cell hemoglobinopathy. Setting: Simulated doctor-patient encounter. Participants: Pediatric residents participating in an educational workshop on how to inform parents about positive newborn screening test results. Main Outcome Measures: Abstraction used an explicit-criteria data dictionary with definitions for 5 different ways to assess understanding. A "partial" designation was used for leading syntax or no pause for response. Results: Interabstractor reliability over 59 transcripts (2 per resident) was κ=0.93. Only 26 of 59 transcripts (44.1%) met definite criteria for at least 1 assessment of understanding. Most assessments were the less effective close-ended (37.3% of transcripts) and "OK?" question types (32.2% of transcripts). Only 3 transcripts met definite criteria for an open-ended assessment and no transcripts included a request for a teach-back, the type thought to be most effective. Four transcripts (6.8%) included an advance request for questions. With partial-criteria assessments included, an additional 31 transcripts (52%) were identified. Conclusions: The small number of assessments of understanding and the high fraction of less effective assessments do not bode well for parental understanding, especially for parents with limited health literacy. Training programs should address assessments of understanding, but quality improvement activities using these types of assessment methods may also be needed.