Up to 1,600 university staff in Northern Ireland are taking strike action as part of a UK-wide pay campaign.
The academics' union says salaries have declined by 40% in 20 years
Lectures for more than 30,000 students have been cancelled in the province's universities on Wednesday and further disprution is expected on Friday.
The Association of University Teachers (AUT) has rejected a pay rise of 3.44% this year and 3% next year.
The academics' union is also protesting against plans to end nationwide pay negotiations and to change the grades of some staff.
It says that their salaries have declined by 40% compared with the rest of the workforce over the last 20 years while the number of students being taught has doubled.
Workers in libraries, computing and administration are also likely to be affected.
The union claims a 6.44% pay rise offer over two years would not tackle the shortfall in their salaries and would not compensate for proposed changes to pay and conditions.
Renee Prendergast, vice president of the AUT at Queen's University Belfast, said she believed academics were earning about 40% less than workers in comparable professions.
Association told its members to boycott student assessments
"One of our problems with the new proposals is that it would take even longer than it does at the moment to move up the scale," she said.
The association has also told its members to boycott student assessments as well as marking and setting examinations from 1 March onwards.