60 pregnant women underwent a double blind trial with calcium or ascorbic acid (1 g twice daily) as treatment for leg cramps. There was no significant difference between the two treatment groups with respect to clinical improvement. In 14 out of 60 patients the symptoms were totally abolished and in another 27 patients the symptoms were significantly decreased by the treatment (irrespective of drug used). In 17 patients the symptoms were unaffected while only two patients experienced an increase in frequency of their leg cramps during therapy. Serum total and ionized calcium concentrations, serum total magnesium and albumin concentrations were determined and were not significantly changed throughout therapy in any of the groups. No biochemical differences were found between the different treatment regimens or between those patients relieved or not relieved of their symptoms. Serum magnesium concentrations were at or just below the lower normal limit (for non pregnant women) in treated women and pregnant controls.