OBJECTIVES: This study was designed to answer the question: Does the contact of the human organism with the Earth via a copper conductor affect physiologic processes? Subjects and experiments: Five (5) experiments are presented: experiment 1-effect of earthing on calcium-phosphate homeostasis and serum concentrations of iron (N?=?84 participants); experiment 2-effect of earthing on serum concentrations of electrolytes (N?=?28); experiment 3-effect of earthing on thyroid function (N?=?12); experiment 4-effect of earthing on glucose concentration (N?=?12); experiment 5-effect of earthing on immune response to vaccine (N?=?32). Subjects were divided into two groups. One (1) group of people was earthed, while the second group remained without contact with the Earth. Blood and urine samples were examined. RESULTS: Earthing of an electrically insulated human organism during night rest causes lowering of serum concentrations of iron, ionized calcium, inorganic phosphorus, and reduction of renal excretion of calcium and phosphorus. Earthing during night rest decreases free tri-iodothyronine and increases free thyroxine and thyroid-stimulating hormone. The continuous earthing of the human body decreases blood glucose in patients with diabetes. Earthing decreases sodium, potassium, magnesium, iron, total protein, and albumin concentrations while the levels of transferrin, ferritin, and globulins ?1, ?2, ?, and ? increase. These results are statistically significant. CONCLUSIONS: Earthing the human body influences human physiologic processes. This influence is observed during night relaxation and during physical activity. Effect of the earthing on calcium-phosphate homeostasis is the opposite of that which occurs in states of weightlessness. It also increases the activity of catabolic processes. It may be the primary factor regulating endocrine and nervous systems.