Potential sperm donors should not be concerned about the knock-on effects of new laws allowing them to be traced by offspring, research suggests.
A shortage of sperm donations threatens the services
Fears that they will be contacted to act as a parent or provide financial support are completely unfounded, a Human Reproduction study shows.
It involved surveys of young people conceived through open-identity donors at the Sperm Bank of California.
Those requesting donor information did so to discover more about themselves.
None of the 29 young people, aged 12-17, who were questioned wanted to contact their biological father to request financial support.
The most common reason for wanting to know the donor's identity was to find out what the donor was like and, for many, the chance to see if it would help them to learn more about themselves.
Lead researcher Dr Joanna Scheib, of the University of California, said: "The stereotypical concern of offspring showing up on the donor's doorstep is inaccurate and does not reflect the intentions of the actual youths going through the identity-release process.
"While it appeared that the children were very curious and eager to learn more about their donor, they were also concerned about respecting his privacy and not intruding on his life."
The US has operated a policy of open-identity sperm donation - presumed consent to provide donor identities to offspring once they have reached the age of 18 if requested - for many years.
This is the first study to gauge the opinions of adolescents who are nearing the age when their biological father's identity can be released to them.
The UK will also require open-identity for donations from April 2005.
Olivia Montuschi from the Donor Conception Network said the authors findings correlated with their own experience in the UK.
"All the evidence from our organisation, which has been in existence for 12 years now, is that whilst a proportion of young people are interested in their donors, particularly knowing something about who they are as people, how they tick, what their values are in life, they are not interested in them as fathers at all.
"They would particularly like to know what the person looks like.
"They would like to see a photograph because, similar to adopted people, they would like to see if possible their own looks reflected in someone else, especially if they do not look like their parents.
"Or they would like to find out if certain traits or skills, such as being artistic, have come from their donor, for example, and something about what the donor's beliefs are."
Dr Allan Pacey, of the British Fertility Society, said the study should go "part of the way" to reassure future donors that donor conceived children would take a measured and responsible view about contacting them.
However, he said: "It is of some concern that four out of five donor conceived people were likely to try and contact the donor as this may mean that even if future donors come forward, they may place limits on the number of births that can be achieved from their donations."
She said as people got older they then might become interested to find out their donor's health status.
Susannah, 18, who was conceived using sperm donation in the UK said: "I believe it is a basic human right for a donor insemination conceived person to know about her donor.
"I respect that he may not want to be named, but I think donors should at least put down details of what they look like, the colour of their eyes and their height - basic things like that.
"If I knew what colour eyes my donor father had that would help me let go of a breath I have been holding on to for ages and make me feel better.
"It really is about knowing these tiny details. It is the little things that matter.
"I'd also like to know what my donor likes and dislikes, his hobbies, favourite TV shows, his views on life, what he believes in and what his values are.
"I believe these things are the key to understanding myself.
"It is hard enough as you are growing up to find out who you really are without not knowing the full genetic equation."
Most of the young people in the study had been told about their conception origins at an early age, which experts believe is important.