This paper comprises a study of the electrostatic potentials generated on the surface of the scrotal area when different types of textile fabric were worn. 21 healthy volunteers were divided into 3 equal groups. The first group was dressed in underpants made of 100% polyester, the second of 100% cotton, and the third of a 50:50% polyester:cotton mixture. With an electrostatic kilovoltmeter, the electrostatic potentials were measured 1 h after wearing the pants once at daytime and a second time at night. The test was repeated 4 times, each on a separate day. No electrostatic potentials were detected on the cotton underpants. The polyester pants showed the highest potentials (mean 338.9 +/- 25 SD Volt cm-2) while the mixed polyester:cotton pants produced less than half that level (mean 148.3 +/- 16 SD Volt cm-2). The readings at daytime were higher than at night, probably due to the higher temperature during the day. The accumulated electrostatic charges on the pants are due to the friction of the pants with the skin. As a result of friction, equal and opposite charges are accumulated on the skin surface and on the inner surface of the pants facing the skin. Eventually, an 'electrostatic field' is produced traversing the scrotal contents and may disturb the testicles and/or epididymis leading to disordered spermatogenesis.