Two groups of patients on regular lithium therapy were studied to find out the stability in values of serum lithium over a period of time. Serum samples of one group was stored at -4°C while that of other group at room temperature. These samples were subsequently analysed over a period of eight days and subjected to statistical analysis. It was seen that values on the first day did not differ significantly from values of subsequent days. Implications of this findings are discussed in Indian conditions as lithium estimation facilities are available only at a few centres.