We correlated clinical symptom complexes of drugs (toxidromes) to results of 204 consecutive toxicological screens ordered in our emergency-department. The toxidromes were divided into eight categories: sedative hypnotic, narcotic, stimulant, coma-apnea-seizure, hallucinogenic, anticholinergic, unknown, and "no drugs." Emergency medicine nurses, clinical pharmacists, and medical residents were asked to choose one or more of the above toxidromes independently when ordering the toxicology screen. The nurses achieved the highest symptom complex recognition of the drug (55 of 61, 88%) followed by medical residents (76 of 90, 84%) and clinical pharmacists (27 of 34, 79.4%), but the differences were not statistically significant. We conclude that the major determinant in selecting correct toxidromes is clinical experience of the practitioners. Given the percentages of toxidrome recognition, it should be possible to increase efficiency of laboratory use by ordering tests only for the drugs clinically suspected in a particular toxic patient.