Funding gaps are beginning to emerge in the health service, according to the public sector spending watchdog.
The NHS faces funding gaps
Auditor General Robert Black said the Scottish NHS was on course for a £183m deficit in the current financial year.
He said it was "difficult to assess" whether the NHS was delivering value for money.
Mr Black's report set out "financial weaknesses" in the service, which spent £8bn last year, but the health minister pointed to progress in key areas.
Mr Black said that unless the health service achieved significant efficiencies there was real risk of a funding gap building up.
He said: "Certainly we see funding gaps beginning to emerge next year if the same level of service is going to be sustained.
"So the NHS needs to find ways of generating savings that carry through from one year to the next, rather than simply crisis measures in a single year."
Audit Scotland's report, covering the financial year 2004/05, found that the health service was performing well in some areas.
The watchdog said waiting times had reduced dramatically, although the report warned it would be difficult to reduce them any further.
Deaths from cancer, heart disease and stroke were also falling, although they were still higher than the rest of the UK.
The executive had met its target to reduce the number of smokers six years early.
But the report said it was unlikely to meet targets on reducing alcohol consumption.
Only about a third of people in Scotland exercised enough and the number of suicides was rising.
The report said the executive's health department had overspent its £8bn budget by £32m last year - despite predictions of a surplus.
Health Minister Andy Kerr said progress had been made
The health boards covering Argyll and Clyde, Grampian, Lanarkshire and the Western Isles had a combined overspend of £91.1m, up 50% on the previous year.
While the other 11 boards were in the black, there was a predicted funding gap of £183m this year.
Health Minister Andy Kerr said the report underlined the progress that had been made, with reductions in waiting times and in deaths from the three main killer diseases.
He said the executive had also acted to improve financial performance by setting up a group to scrutinise boards more closely and intervene if necessary.
"On top of that, we now hold annual reviews for each board to scrutinise their performance in public, and we have also introduced more rigorous financial monitoring for the health department itself," said Mr Kerr.
Conservative health spokeswoman Dr Nanette Milne said a lot more needed to be done.
"We already know the executive is not going to reach its cancer waiting time targets, MRSA is still constant, performance in monitoring mental health - an executive priority - is 'weak', suicides have increased and the figures for delayed discharges are also up," she said.
Scottish National Party health spokeswoman Shona Robison said the "root cause" of NHS boards' financial problems needed to be tackled.
"That means that the executive cannot pass the buck, they must intervene at an early stage to sort out the financial difficulties otherwise it is patients who will suffer through cuts to services," she said.
Health service workers' union, Unison, said it was pleased with the positive aspects outlined in the report.
However, Scottish health organiser Glyn Hawkins said: "We are pleased that increased investment is achieving better clinical outcomes and congratulate hard-working staff for delivering these improvements.
"However, some of the financial and staffing information point to what Unison has been saying for some time - that we need to increase training, pay and flexibility in conditions to provide staff trained to deliver on other targets."