The Abu-Saad Pediatric Pain Assessment Tool consists of 30 word descriptors in the sensory, affective and evaluative domains as well as a 10 cm scale that measures present and worst pain experienced by the child. In the first phase of the study an inventory was carried out of pain word descriptors used by hospitalized Dutch children. In the second phase, these word descriptors were given an intensity value on the 10 cm scale by 355 children. An alpha reliability coefficient of 0.83 supported instrument homogeneity. Factor analysis (N - 355) was used to investigate construct validity. A three-factor solution was carried out to evaluate the validity of the three dimensions of pain. Factor 1 consisted of items in the affective and evaluative domains and factors 2 and 3 items from the sensory domain. Ultimately a two-factor solution provided the most intelligible conceptual pattern with the least loss of information. Conceptual composition and discussion of these factors are described and elaborated.