It was the aim of this paper to assess whether GnRH agonist and add-back therapy is an important post operative and long-term therapeutical supplement in the treatment of genital endometriosis, especially in cases of chronic pain. Although its effectiveness with regard to the relief of pain is not better than other therapeutical options, the spectrum of side effects is acceptable. Un-desired side effects of GnRH agonists are reversible and can be minimised under the synchronised application of an add-back therapy. In patients with symptomatic endometriosis the effectiveness of GnRH agonist therapy can remain and simultaneously the hypoestrogenic side-effects can be covered by the appropriate add-back therapy. In our investigations a useful combination treatment of leuprolide acetate depot (3.75 mg per month) and tibolone (2.5 mg per day) over a period of 3-6 months was found. The analyses of Hornstein et al. 1998 and Surrey et al. 2002 clearly demonstrate that a significant reduction in pain with few side effects results when from the first day of treatment with leuprolide acetate depot an add-back scheme of 5 mg norethindrone acetate per day is applied.