Two calves developed a CNS syndrome characterized by hyperesthesia, tremors, and incoordination while nursing dams that had been feeding on ammoniated forage. To increase digestibility, intake, and nitrogen content, low-quality forages were ammoniated at a rate of 3% dry weight. However, a CNS syndrome of unknown cause has been observed in cows and calves nursing cows that have ingested ammoniated forage. Serum electrolytes, glucose, and blood differentials of the 2 calves in this report were normal. However, the older calf had high serum and CSF ammonia concentrations. Both calves, sedated with acepromazine and given thiamine injections, were clinically normal 12 hours later.