Lithium in serum was determined by a plasma emissionspectrophotometer "Spectraspan" (low power d.c. plasma are, operating on argon). The opitimum condition for ashing of serum by low temperature was studied. The influences of hydrochloric acid and several metallic ions (Na, K, Mg, Ca) on emission intensity were examined. There was a linear relationship between emission intensity and lithium content from 0 to 10μg/ml. Lithum in serum was easily determined by standard addition method. Precision, coefficient of variance and recovery of known amount of lithium added to the sample for 12 replicate analyses were 0.093μg/ml, 1.85%, 99-104%, respectively. Significantly positive correlationship was observed between emission spectrophotometry using spectraspan and atomic absoption spectrophotometry.