In an investigation of 113 cases of clenbuterol poisoning in Catalonia, Spain, in 1992, more than 50 percent of those affected were found to have had symptoms of nervousness, tachycardia, muscle tremors, myalgia, and headache. There was no significant difference in the distribution of symptoms according to sex (P = 0.97). The period of incubation varied between 15 minutes and 6 hours and the duration of symptoms between 90 minutes and 6 days. Clenbuterol was detected in 47 urine samples in amounts ranging from 11 to 486 parts per billion. No traces of clenbuterol were found in serum samples. Intoxication occurred in association with the ingestion of veal liver, irrespective of the way in which the liver had been cooked. The association between consuming liver and falling ill was statistically significant (P < 0.0001). In one family, the suspected source of intoxication was meat (veal tongue) and in another canneloni. None of the patients died as a result of the intoxication. The findings reinforce the need to uphold the prohibition of the use of clenbuterol in cattle farming in those countries and communities where it already exists and to contemplate a stricter regulation of its therapeutic use.