Headed by Univ.-Prof. Dr. Martin Imhof, this open comparative study was carried out at the Fertility Centre at the Vienna International Medical Clinic in Austria between January 2006 and October 2010. A group of 132 sub-fertile men (treatment arm) was invited to take two daily capsules of the active ingredient (PROfertil®) for a period of three months between the first and subsequent sperm analysis. Each capsule with the active ingredient contained L-carnitine, L-arginine, zinc, vitamin E, glutathione, folic acid, selenium and coenzyme Q10. The control group consisted of sub-fertile men who were not given the active ingredient (n = 73). The relevant target measurement method was standardized sperm analysis, carried out at the beginning and after three months of treatment. The inclusion criteria were age >18 and < 65 years, infertility for a year and at least two abnormal semen analyses (also called spermiogram or sperm test) prior to the study. Exclusion criteria were varicose veins, infections, aspermia or hormonal disorders.