The objective of this study was to evaluate the relationship between trace and toxic amounts of zinc (Zn) in biological samples (blood and urine) and the smoking habits of hypertensive patients and healthy control subjects in Valladolid (Spain). In order to compare biological samples, the concentrations of these samples were measured using inductively coupled plasma mass spectrometry. The limits of detection for Zn in blood plasma ranged between 4.22 and 17.34 μmol l(-1) and were <0.08 μmol g(-1) creatinine in urine. The results of this study indicate that the highest mean values of serum Zn were found in non-hypertensive nonsmokers (13.39±4.35 μmol l(-1)), whereas the highest urine Zn values were observed in hypertensive nonsmokers (2.78±2.13 μmol l(-1)). Higher Zn serum/urine quotient levels were observed in non-hypertensive and nonsmoking women, whereas lower levels were noted in non-hypertensive and smoking women (P=0.012). This study identified a correlation between Zn serum/urine quotients and cotinine levels (a marker of smoking), a correlation that suggests that smoking lowers the Zn serum/urine quotient, which was lower in hypertensive subjects than in control subjects.