OBJECTIVES Male reproductive health has deteriorated in recent decades. It is proposed that increased testicular temperature in early childhood, due to the use of modern disposable plastic lined nappies (diapers), could be an important factor contributing to this decline.

STUDY DESIGN Scrotal skin temperature was measured non-invasively in 48 healthy children aged 0–55 months (three age groups) for two 24 hour periods in randomised order (either cotton or disposable plastic lined nappies) using a portable, miniature recorder.

RESULTS Mean 24 hour scrotal temperature (2880 measurements) was significantly higher in all age groups during the periods of plastic nappy use than with cotton nappies (p < 0.001). The rectoscrotal temperature difference was significantly higher with cotton than with plastic nappy use (p < 0.01).

CONCLUSIONS Scrotal hypothermia is an important factor for normal spermatogenesis. This study shows that scrotal temperature, which closely reflects testicular temperature, is increased in boys wearing disposable plastic lined nappies. The physiological testicular cooling mechanism is blunted and often completely abolished during plastic nappy use. The present results establish the basis for further research on the impact of increased testicular temperature in infancy on later spermatogenesis.