Scottish Census Day 2011 survey begins
Millions of Scots are expected to fill in questionnaires on Sunday for the 2011 census.
More than 2.5 million forms were sent out to homes across Scotland in preparation for Census Day.
The population survey is collecting information on topics such as age, gender and health to help plan services like housing, hospitals and schools.
Citizens are required to complete the questionnaire and could face a fine of up to £1,000 if they fail to comply.
The form must cover any people living or staying with a householder on the night of 27 March.
Residents are expected to return their answers to the census organisers as soon as possible.
Personal data from the questionnaires will be kept confidential for 100 years.
For the first time, citizens have the option of completing the census online.
Disabled and older people have raised concerns about how difficult the form is to complete.
But Scotland's census organisers, the General Register Office for Scotland, said there would be extra support available online and on the phone over the few weeks. The helpline number in Scotland is 0300 1231702.
A website was set up for Scotland's Census 2011 to help people decide whether or not they speak or understand the Scots language.
The Aye Can site was prompted by the inclusion, for the first time, of a question about language.
The survey asks those living north of the border if they can understand, speak, read and/or write Scots.
The language includes Scottish dialects such as Glaswegian, Doric, Buchan, Dundonian or Shetland.