The circumstances surrounding the arrest or accident were examined, together with any observations by the arresting officer regarding behavioral irregularities. The investigators also made a determination of culpability. Most of the arrests resulted from accidents in which the driver was determined to be culpable. typical driving behaviors included drifting out of the lane of travel, erratic driving, weaving, speeding, drifting off the road, and high speed collisions. Behavioral manifestations of methamphetamine use in arrestees included rapid or confused speech, rapid pulse, agitation, paranoia, dilated pupils, and violent or aggressive attitude. Combined alcohol and methamphetamine use was uncommon; however, use of marijuana was evident in approximately one-third of the cases. In addition to impairing judgment and increasing risk-taking, the effects of withdrawal from methamphetamine use, including fatigue, hypersomnolence, and depression, are likely contributors to many of these accidents. A consideration of the literature and the cases discussed leads to the conclusion that methamphetamine at any concentration is likely to produce symptoms that are inconsistent with safe driving. 2 tables, 1 figure, and 37 references