The levels of magnesium (Mg), zinc (Zn) and copper (Cu) in the plasma, erythrocytes (RBC) and polymorphonuclear (PMN) and lymphocyte (L), leukocytes (WBC) of 45 diabetic children were compared to those of 12 normal children and were related to the diabetic control via HbA1 and fasting blood sugar (FBS) assessments. Mineral levels were determined via Zeeman-effect atomic absorption spectrophotometry following separation of plasma, RBC, and WBC fractions (PMN vs. M). ANOVA (four-way, blood components, by two-way, diabetic vs. normal children) was significant for Mg only (F = 4.60, P < 0.004). Plasma Mg and M-WBC Mg were significantly lower in children with diabetes (780 +/- 16 vs. 860 +/- 29 mumol/l and 519 +/- 33 vs. 866 +/- 86 micrograms/10(10) cells, respectively). RBC Zn was significantly lower in diabetic youngsters by t-test (0.48 +/- 0.012 vs. 0.57 +/- 0.046 per mumol/g Hgb, t = 2.79, P < 0.004), but the ANOVA for Zn was not significant. Cu level differences were not significant. HbA1 was predicted only by PMN-WBC Mg (F = 8.78, P < 0.04) and FBS by none. In conclusion, the mineral status of these diabetic children was altered in regard to Mg, but was mainly independent of diabetic control.