The objective of this paper is to report on the reliability and validity of a knowledge, attitude and practice instrument used among young primary school children. The instrument was developed as an evaluation tool in the HELIC study and consisted of 23 knowledge, 11 attitude and 10 practice items. A total of 335 Year 2 students from 4 randomly selected primary schools in Selangor and Wilayah Persekutuan participated in the HELIC study. Students were divided into small groups and an enumerator verbally administered the instrument to each group. Reliability for each construct (knowledge, attitude and practice) was estimated as item to total score correlation and internal consistency (Cronbach's alpha). Construct validity was determined through factor analysis and Pearson correlation. Results indicated that 3 attitude and 3 practice items did not correlate significantly to the total score (p>0.05). However, the deletion of these items did not significantly alter the Cronbach's alpha coefficients. Internal consistency was good for knowledge (a=0.68) but low for attitude (a=0.37) and practice (a=0.36) constructs. Based on factor analysis, 5 factor-solutions emerged for knowledge and 4 factor solutions for attitude and practice. Sufficient variance was obtained for the factors in knowledge (51.7%), attitude (51.2% and practice (51.0%). There were also significant positive correlations among the constructs ( ~ 4 . 0 1 ) . In conclusion, the instrument was valid and reliable, especially for the knowledge construct. Further improvements, particularly on the attitude and practice constructs, are needed in order for the instrument to be an effective assessment or evaluation tool in various settings.