The concentration of cadmium, lead, copper and zinc in urine of heavy khat- chewers with matched normal controls was investigated by differential pulsed anodic stripping voltammetry (DPASV). The analysis showed that urinary cadmium, lead, copper and zinc of regular khat users were significantly higher than those of the controls. The peak for urinary copper levels was attained after about 2-3 h following khat chewing. The height of the peak was found to depend on the type and amount of khat digested. In contrast, the circadian rhythm of urinary zinc demonstrated a remarkable and progressive decline of urinary zinc during khat chewing that is independent of zinc nutritional status. Cathinone, the active principle of khat may resemble penicillamine and other chelators in their strong capability to form copper complexes and that the interaction between zinc and copper is mutually antagonisticThe concentration of cadmium, lead, copper and zinc in urine of heavy khat- chewers with matched normal controls was investigated by differential pulsed anodic stripping voltammetry (DPASV). The analysis showed that urinary cadmium, lead, copper and zinc of regular khat users were significantly higher than those of the controls. The peak for urinary copper levels was attained after about 2-3 h following khat chewing. The height of the peak was found to depend on the type and amount of khat digested. In contrast, the circadian rhythm of urinary zinc demonstrated a remarkable and progressive decline of urinary zinc during khat chewing that is independent of zinc nutritional status. Cathinone, the active principle of khat may resemble penicillamine and other chelators in their strong capability to form copper complexes and that the interaction between zinc and copper is mutually antagonistic