The aims of this study were to examine whether objective measurements of the 10-minute drooling quotient (DQ10) and the 5-minute drooling quotient (DQ5) are interchangeable; to assess agreement between the measurements and their accuracy in classifying drooling severity; and to develop a time-efficient clinical assessment. METHOD: The study cohort included 162 children (61 females, 101 males; mean age 11 y 6 mo, SD 4 y 5 mo, range 3 y 9 mo-22 y 1 mo) suffering from moderate to profuse drooling. One hundred and twenty-four had cerebral palsy and 38 had other developmental disabilities. Seventy-four of the participants were ambulant and 88 non-ambulant. The original DQ10 was recalculated into a 5-minute score (DQ5). Assessments were undertaken while the participants were in a rest situation (DQ(R)) and while they were active (DQ(A)). Agreement in scores was quantified using intraclass correlations and Bland-Altman plots. To classify drooling, area under the receiver operating characteristic curve analysis was used to compare accuracy of the DQ10 and DQ5 at rest and during activity. RESULTS: Agreement between DQ10A, and DQ5(A), and between DQ10(R) and DQ5(R) was high (intraclass correlation coefficient >0.90). Moderate agreement existed between DQ(A) and DQ(R). DQ(A) scores were more accurate in classifying children's drooling behaviour. For DQ5(A), a cut-off point of 18 or more (drooling episodes/observation time) might indicate 'constant drooling'. INTERPRETATION: The DQ10 and DQ5 can be used interchangeably. DQ(A) is most discriminative for drooling severity. For evaluating treatment efficiency the cut-off point can be used. For clinical and research purposes, the DQ5 is time efficient and cost saving while validity, and intrarater and interrater reliability are preserved. CI - (c) The Authors. Developmental Medicine & Child Neurology (c) 2012 Mac Keith Press.