Few employees of Microsoft and other big companies such as Intel in Ireland have reached millionaire status despite the relative success of their US counterparts.

There has been speculation that Microsoft's Irish operation has produced 18 millionaires but informed sources suggest this figure is probably closer to six.

Some variables stand between Irish employees and potential fortunes amassed from stock options. According to one former Microsoft Ireland employee, the only people who stood to benefit greatly were those serving at a very senior level for more than 10 years. There could be no more than six such people.

Microsoft has only been located in Ireland since 1985 barely a sufficient length of time for exercised stock options to hit the £1 million mark.

It takes at least 4 1/2 years to exercise Microsoft share options completely. They cannot be realised in year one, and after that only one-eighth of the stocks can be exercised every six months. The purchase price of the stock is also a significant factor. Many of the senior US staff would have purchased their stocks during an initial period of very high growth after the company went public in 1986. They are the ones who became millionaires.

Microsoft's operation in Ireland employs 1,200 people, with most involved in the manufacturing or localisation process. The more skilled or valuable the employee is to the company, the more stock options they will be offered. However, highly-talented researchers or technicians are more likely to be located in the US at Microsoft's headquarters in Seattle.

More recently Bill Gates has been offering hundreds of thousands of stock options to potential employees in a bid to employ the best of US talent. Indeed, the value of stock options is becoming more important than salary.

Mr Liam Cahill, head of Public Affairs at Intel Ireland, said becoming a millionaire depends on the number of stock options offered, the price at which they are granted, and the price at which those options are exercised. "I could quite happily say no employee of Intel Ireland has sufficient access to stock options here to bring them up to the category of millionaire," he added.

The stock options an average Intel employee receives each year would be in the region of several hundred. A rough estimate suggests an employee would need options on about 21,000 shares to be worth £1 million. Mr Cahill said it would be "highly fanciful" to imagine any Irish employees had become a millionaire at this stage.

A former Intel employee says the prospect will become a reality in the future but will take a minimum of 10 years and rely heavily on the company continuing to be profitable. With stock options available to all employees, the successful exercise of those options relies heavily on being able to afford to hold on to the stock.