There is little information on the prevalence and clinical presentation of acid-base abnormalities associated with cocaine toxicity. To address these issues, arterial blood gas results were evaluated in 156 cocaine-associated emergency department patient visits. Arterial blood gas results were obtained as part of the patient's clinical assessment. The majority of patients (52%) had a normal pH (7.35 to 7.45). Thirty-three percent of patients were acidotic, with a pH between 6.4 and 7.35. In 33 patients the acidosis was metabolic, with a HCO3- of 14 +/- 6 mmol/L. The acidosis was primarily respiratory in 18 patients, with evidence of hypoventilation. Hypoventilation was generally secondary to chest trauma or decreased mental status. Alkalosis (pH > 7.45) was observed in 15% of patients, and was usually respiratory, as evidenced by tachypnea and a low PCO2. These results indicate that metabolic and respiratory acid-base abnormalities are common during cocaine toxicity. Acidosis and alkalosis were associated with numerous patient presentations, including chest pain, shortness of breath, decreased mental status, trauma, and seizures. Acid-base abnormalities do not appear to be associated with a specific route of cocaine self-administration. Patients with a history of potential cocaine toxicity should be evaluated for acid-base abnormalities.