Data are submitted from the analysis of factors of the pathogenesis of multinodular non-toxic goiter in 380 persons. Of these, 256 underwent surgery. An apparent iodine deficiency in the body (in two thirds of patients) has been found out to be an important cause of development, progression and recurrence of goiter. Only 5 to 14 percent of patients, predominantly those presenting with recurrent goiter, demonstrated an elevated level of thyrotrophin. More commonly seen in these patients is inherited predisposition to goiter. The authors attach much value to urine iodine levels, and consider it mandatory that a correction of iodine deficiency be carried off with available drugs both during the conservative treatment and in recurrences.