The Nancy Padian study, (held in California from 1985 to 1997), was the longest and most comprensive study on transmission of HIV (or transmission of sero-positive-ness) between hetero-sexual partners in couples, who were 'assymetric', (one partner was sero-positive, the other wasn't).

In the abstract of the study one can read that the chances of HIV transmission were as following:

- Male to female: about 1 in 1,000 (more exactly 0.9 in 1,000)

- Female to male: +- 8 times less probable, so about 1 in 8,000 (or more exactly 1 in 7,200)

Hence, apparently during the whole period of 10 years of trial, it is said that "no" sero-conversions took place.

My question is: can anyone please shine a ligh on this..?

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The study itself can be found here, (the full text in 'pdf file', is accessable with a link at the bottom of the article's abstract): " Academic.oup.com/aje/article/146/4/350/60711 " (copy & paste this link to the abstract, into your browser).