Absence from work cost British business a record £10.5bn in 1999, finds the Confederation of British industry and PP Healthcare.
The figure boils down to £438 per worker, compared to £426 per worker in 1998 when absence cost British business £10.2bn.
It suggests that 187 million working days were lost in 1999.
A CBI spokesperson said the rise could reflect the rise in average earnings rather than an increase in absence itself.
Manual employees took off more time than non-manual employees, but absence among both groups declined.
Small firms had lower absence rates than large firms.
Around nine days were lost per employee among companies employing more than 500 employees compared to 4.8 days among companies employing fewer than 50 employees.
Public sector employees took 9.9 days off on average, which is, on average, 2.8 days fewer than their private sector counterparts (7.1 days).
CBI's Human Resources Policy Director John Cridland said: "Absence is a huge cost to business and the worst performing firms have twice the absence rates of the best ones.
"Most absence is caused by genuine minor illness, but it is important for firms to ensure unnecessary absence is reduced – benchmarking performance against similar firms will reveal problem areas."