Objective: To investigate the relationship between stunting and levels of overweight/obesity among South African school children, using two definitions of overweight and obesity, based on the WHO and International Obesity Task Force (IOTF) criteria. Design: Cross-sectional descriptive analysis of the nutritional status of primary school children, using primary data from a rural community-based study undertaken in 1995 and secondary data from the South African National Primary Schools (SANPS) survey conducted in 1994. Stunting was measured according to the WHO definition of -2 Z scores height-for-age. Two sets of criteria were used to measure overweight and obesity—the WHO/NCHS standard based on the 85th and 95th centiles and the IOTF criteria. Setting: The primary data source was from a rural KwaZulu-Natal community based survey. The secondary data source SANPS consisted of data at National and Provincial level; for this study only data from the province of KwaZulu-Natal was considered. Subjects: Primary school children aged between 8 and 11 y of age; 802 from the primary data source and 24 391 from the secondary source. Results: Moderate stunting ranged from 2.9 to 40.2%, and mild stunting ranged from 31.4 to 75%. The prevalence of overweight ranged from 0.4 to 13.3% (WHO criteria) and from 0.4 to 11.9% using the IOTF criteria; while obesity ranged from 0.1 to 3.7% (WHO) and from 0.1 to 1.5% (IOTF criteria). The prevalence of overweight and obesity was observed to be higher using the WHO definition than that of IOTF (0.05 < P < 0.10). However, good kappa coefficient (κ) levels of agreement were observed between the WHO and IOTF definitions of overweight and obesity (κ > 0.55, in all cases). The levels of agreement in all cases were less for obesity than overweight (both ranged from 0.55 to 1.0). Females were observed to have higher κ levels than their male counterparts; they also had higher prevalence levels of overweight and obesity... [ABSTRACT FROM AUTHOR]