Overdose with calcium channel blockers (CCBs) may lead to serious complications. CCBs act by blocking calcium entry into the cell, thus lowering intracellular calcium ([Ca2+]i). [Ca2+]i during CCB overdose has not yet been reported. We measured [Ca2+]i in lymphocytes of a patient with acute verapamil overdose with a complex clinical picture. A 59-year-old woman was admitted after a suicidal ingestion of 7200 mg of a sustained-release verapamil preparation. She presented with hypotension, complete atrioventricular block, stupor, hypokalemia, and hyperglycemia. Acute oliguric renal failure, acute pancreatitis, and the adult respiratory distress syndrome further complicated her medical course. Treatment was supportive and she recovered completely. Intracellular calcium ([Ca2+]i) was measured in the patient's lymphocytes using a spectrofluorometer with the calcium-sensitive dye Fura-2-acetoxymethyl ester. Thirty nine hours after the ingestion, [Ca2+]i was low at 52 nM (compared with 80 nM in a healthy control subject). Lymphocytic [Ca2+]i did not respond to stimulation with phytohemagglutinin (PHA). Fourteen days after the verapamil overdose, after the patient had recovered completely, lymphocytic [Ca2+]i was still low at 55 nM. At this time, there was an incomplete response to PHA in the lymphocytes. Three months after the ingestion, [Ca2+]i was normal, with a normal response to PHA. Verapamil overdose may run a complex clinical course, but full recovery is to be hoped for with full supportive care. Cellular intoxication, as reflected by low lymphocytic [Ca2+]i, is prolonged and lags behind the clinical recovery by weeks.