Basic principles for simulation of acute reference dose (ARfD) setting were defined based on the work of Solecki et al. (2005). The principles are: (1) Appearance of acute toxicity within 24 h after oral administration. (2) Rationale for setting toxicity that appears or could appear after single oral administration. (3) ARfD setting is assumed to be necessary for all pesticides. (4) ARfD setting is not necessary when the value is at or above the cutoff level. (5) The setting basically applies to the general population. (6) ARM is set based on the lowest NOAEL among all the available study data concerning endpoints for acute effects. (7) Effects of exposure during critical periods should be considered as endpoints for ARfD setting. (8) The approach for the safety coefficient is the same as that for acceptable daily intake. (9) If available, human data are acceptable as an endpoint for ARfD setting.