The aim of this study was to examine the validity of the Bruininks-Oseretsky test of motor proficiency - short form (BOTMP-SF) [Bruininks, R. (1978). Bruininks-Oseretsky test of motor proficiency: Examiners manual. Circle Pines, MN] for the assessment of preschool aged children. Three-hundred and eighteen children 48-71months old (M=58.97months, SD=6.73) participated in the study. For the data analysis both an ANOVA and a MANOVA were applied with the total battery score and the 14 item scores being the dependent variables, respectively. Age was found to have a significant effect on both children's total battery score (F(3, 314)=110.65, p<.001, eta(2)=.68) and 13 item scores (minimum F(3, 314)=8.75, p<.001, minimum eta(2)=.145). Although the aforementioned results represent an evidence for the validity of the BOTMP-SF, a closer study on the score of each item revealed a high percentage of zero scores on four items. Task difficulty has caused a floor effect, constituting a threat to the validity of the preschoolers' motor assessment with the above battery. A modification of the battery items is suggested, so that the BOTMP-SF will give valid results for children 4-6years old.