Background. This is a report on the translation and cultural adaptation from English to Turkish languages of a standard HEALTH UTILITIES INDEX (R) (HUI (R)) questionnaire for interviewer-administration and proxy assessment of patients' health status, and its use for assessing 50 consecutive pediatric oncology patients during periods of and subsequent recovery from neutropenia. Procedure. Preparation of the Turkish-language questionnaire was a collaborative effort by physician-researchers in Turkey, senior Health Utilities, Inc. staff with extensive experience in the development and translation of HUI questionnaires, and Turkish-born residents of Canada. Standard HUI questionnaires cover both HUI Mark 2 (HUI2) and HUI Mark 3 (HUI3). Results. The mean improvement in overall health-related quality of life (HRQL) scores between neutropenic and non-neutropenic phases was clinically important according to both HUI2 and HUI3 instruments. Single-attribute utility scores showed clinically important size improvements between phases for HUI2 mobility, emotion, and HUI2 self-care. Significant reductions in disability rates between phases were also detected for pain (HUI2 and HUI3 rate decreases of 30%, P < 0.001) and HUI3 ambulation (rate decline of 14%, P = 0.020). Conclusions. The study results provide evidence that the Turkish-language questionnaire is acceptable, valid and useful for collecting parental assessments of health-status among young cancer patients in Turkey. Neutropenia was associated with important deficits in overall HRQL and disabilities in ambulation/mobility, emotion, self-care, and pain. Treatment plans should include strategies for addressing emotion and pain problems to improve the HRQL of neutropenic patients. Pediatr Blood Cancer Pediatr Blood Cancer 2011;56:812-817. (c) 2011 Wiley-Liss, Inc.