A retrospective six-month study of serum calcium and albumin in patients treated at the Kuala Lumpur Hospital was carried out. There were 19,291 subjects, of which the prevalences of hypocalcemia (corrected serum calcium of < or = 2.1 mmol/l) and hypercalcemia (corrected serum calcium of > 2.7 mmol/l) were 18.0% (3460 subjects) and 2.4% (468 subjects) respectively. Persistent hypocalcemia (a minimum of first two consecutive corrected serum calcium of < or = 2.1 mmol/l) was found in 408/19,291 subjects 2.1%). Serum calcium values of < 2.00 mmol/l were found in 98.5% of this group. Persistent hypercalcemia (a minimum of first two consecutive corrected serum calcium of > 2.7 mmol/l) was found in 108/19,291 subjects (0.5%) and 52/108 subjects (48.1%) had serum calcium values of > or = 3.0 mmol/l. 2902/3460 subjects (83.8%) and 313/468 subjects (66.9%) the hypocalcemia and hypercalcemia groups respectively failed to be retested (singletons). In the hypocalcemia group, 1115/2902 (38.4%) showed corrected serum calcium values of < 2.00 mmol/l), whilst 100/313 subjects (31.9%) of the hypercalcemia group had corrected serum calcium values of > or = 3.00 mmol/l. There were no significant differences between the mean corrected serum calcium between 3 age groups of the test population, namely in childhood ( < or = 65 years).