PIP: Literature data on the mechanism of Laminaria-induced dilatation of the cervix uteri during abortion in the 2nd and 3rd trimesters are reviewed. Laminaria sticks are made of the stems of the algae Laminaria digitata or Laminaria japonica; the standard stick is 6-7 mm in length and 2-3 mm in diameter. Laminaria acts on the cervix uteri by applying the radial force and by removing water from the cervical stroma. One of the mechanisms of action of Laminaria is associated with the stimulation of synthesis and release of endogenous prostaglandins. The most widely used method of sterilization is gammairradiation of individually packaged Laminaria sticks. The thread attached to the proximal end of the stick simplifies its removal. Dilatation of the cervix uteri during 1st trimester requires insertion of 1-4-6 sticks for 6-12-16 hours. The methods of Laminaria insertion during the 2nd trimester vary depending upon the clinical situation. The major disadvantage of Laminaria is acute or spastic pain during insertion. Complications include migration of the Laminaria stick into the vagina or uterus and the risk of infection. Recently developed synthetic Laminaria have a number of advantages over natural Laminaria (guaranteed sterility, uniform shape, more rapid swelling, relative insensitivity to pressure). The most widely used synthetic Laminaria are manufactured from the polyvinyl alcohol (Lamicel, Merocel) and hydrogel polymer (hypan and Dilapan). Merocel and Lamicel are impregnated with magnesium sulfate providing for additional absorption of the fluid.