In most countries, millions of people are relying on herbal medicines as remedy for numerous ailments. In South-East Asia, Eurycoma longifolia Jack, also known as 'Malaysian ginseng' or Tongkat ali, is used to combat stress and disease and to improve physical strength. Moreover, the compounds of the roots of this plant are reported to have aphrodisiac and testosterone enhancing effects in the rat. Considering that human studies are not available, 76 of 320 patients suffering from late-onset hypogonadism (LOH) were given 200 mg of a standardised water-soluble extract of Tongkat ali for 1 month. The Ageing Males' Symptoms (AMS) according to the standardised rating scale and the serum testosterone concentration were taken. Results show that treatment of LOH patients with this Tongkat ali extract significantly (P < 0.0001) improved the AMS score as well as the serum testosterone concentration. While before treatment only 10.5% of the patients did not show any complaint according to the AMS scale and 35.5% had normal testosterone levels, after the completed treatment 71.7% and 90.8% of the patients showed normal values, respectively. Thus, Tongkat ali extract appears to be useful as a supplement in overcoming the symptoms of LOH and for the management of hypogonadism.