There are several mechanisms acting in synergism that can impair sperm characteristics of patients with accessory gland infection. In some cases, conventional sperm variables are disturbed with oligo and/or asthenozoospermia. In other patients, these sperm variables may appear normal, but the functional capacity of spermatozoa may be impaired. In particular, changes in the composition of the sperm membrane may result in reduced acrosome reactivity and capacity to fuse with the oolemma, and oxidative damage of the sperm DNA may induce mutagenesis. Changes in the biochemical make-up of seminal plasma can also reduce the in-vivo fertilizing capacity of spermatozoa, and infection-related disruption of the blood-testis barrier can induce the generation of anti-sperm antibodies and immunological infertility. Many of these functional abnormalities will not become evident upon 'basic semen analysis', which explains why some authors are unable to link infection of the accessory sex glands to subfertility. Also, functional and anatomical damage acquired as a result of infection is often permanent and not reversible by (antibiotic) treatment. Clearly, there are many more aspects of male accessory gland infection that require investigation. Available data should stimulate clinicians to place more emphasis on the prevention of infection-related infertility than on its treatment, as the latter is often unsuccessful.