As per me Indian Institute of Technology Guwahati, Admissions to the PhD programme are held twice a year - in July and January for following Phd program:

Department of Biosciences and Bioengineering
Department of Chemical Engineering
Department of Civil Engineering
Department of Computer Science and Engineering
Department of Design
Department of Electronics and Electrical Engineering
Department of Mechanical Engineering
Department of Humanities and Social Sciences
Department of Mathematics
Department of Chemistry
Department of Physics
Centre for Energy
Centre for the Environment
Centre for Nanotechnology
Centre for Linguistic Science and Technology
Centre for Rural Technology

Admission qualification
Minimum CPI or Percentage of marks in the qualifying degree, with specific requirements for different streams,:

Address
Indian Institute of Technology (IIT), Guwahati
Ambari, Gopinath Bordoloi (GNB) Road,
Guwahati, Kamrup (Distt),
Assam-781001, Email acadoffice@iiitg.ac.in,