An anatomically based assessment scale of handwashing quality with alcohol-based hand rub was designed. Contents of the scale divided each hand into 40 zones. Psychometric measurements were studied in 30 participants (120 hand sides). The scale was both valid (Cronbach α: 0·83 dorsal side and 0·73 palmar side) and reproducible (linear regression R2, 0·91; intraclass correlation coefficient, 0·99).