Nearly 40% of NHS staff in Wales suffer from work-related stress, according to a survey.
The survey was completed by 33,000 NHS staff
A majority of the 33,000 staff who took part also said they do not have enough time to complete their work and that half regularly work unpaid overtime.
But it was also found that 88% felt satisfied with the support they received at work.
The staff survey was commissioned by the Welsh Assembly Government, employers and unions.
It was conducted between September and December 2005.
The survey also found that 16% of those who responded have experienced physical violence in the workplace.
Almost half said that they regularly work unpaid overtime.
Brian Gibbons said the findings on stress were concern
The most common reasons given for doing that were: staff did not want to let down the people they work with; it was necessary to meet deadlines; it was impossible to do the job otherwise; or that they enjoyed the job.
Almost 60% said that they did not have enough time to carry out all their work.
Just over 43% of staff indicated that they often think about leaving their employer, but about 66% said that if they left their current job, they would stay within the NHS.
However, many of the staff who responded said they liked working for the NHS in Wales.
In the survey, 88% of staff felt satisfied with the support they were given to carry out their work, 80% said they always know what their responsibilities and 76% said they have clear objectives for their job.
The 90,000-strong NHS Wales workforce was asked to complete the survey and 33,000 responded.
Welsh Health Minister Brian Gibbons said it was important to hear the views of front-line staff.
He added: "By finding out what they actually think about the service, NHS trusts, NHS Wales and the Welsh Assembly Government can work together in partnership with the trade unions to improve the service for all.
"Overall, it seems as if the majority of staff are happy working for the NHS. I am pleased that staff have been so honest in this survey.
"The fact that 39% of staff have reported suffering work-related stress is a major concern.
"I am also concerned that 16% of staff have faced the prospect of physical violence while at work. This is unacceptable and must not be tolerated."