Senior health service figures will face MSPs investigating a critical report into falsified NHS waiting times.
Chief executives from Glasgow, Tayside and Forth Valley will answer questions from Holyrood's Public Audit Committee less than a month after ministers were warned that trust in official targets has been put at risk.
An investigation by Audit Scotland, which scrutinises public spending, found problems across the country in the way patient waiting times targets are approached by health boards.
The auditors said their work was hampered by a lack of information and because of inadequately-controlled management systems.
The waiting lists problem surfaced in 2011 when NHS Lothian was found to have manipulated waiting time codes, marking patients as unavailable for "social reasons" such as failing to get time off work or being on holiday.
Facing extra pressure to meet shorter 18-week guarantees, it was discovered managers were putting pressure on staff to find ways around the system. This included marking patients as unavailable if they refused to travel to England.
Audit Scotland said it had been hard to trace changes on patient records and identify reasons for the use of waiting time codes. They also found that the use of "social unavailability" increased from 11% in 2008 to just over 30% in 2011.
The levels then dropped off around the time "fiddled" waiting figures were discovered at NHS Lothian.
Internal auditors reported the inappropriate use of unavailability codes at NHS Tayside, on a smaller scale.
At NHS Greater Glasgow and Clyde, auditors said some patients were marked as unavailable for two months. NHS Forth Valley was found to have kept good records in its electronic system but it had the biggest percentage difference between reported and actual waits.