1. 3rd International Congress on Industrial and Applied Mathematics, Hamburg, July 3-7, 1995.
2. National Seminar on Advances in Mathematical, Statistical and Computational Methods in Science and Technology, Indian School of Mines, Dhanbad, Jharkhand, November 29-30, 2001.
3. WSEAS International Conference on Theoretical and Applied Mathematics, Miedzyzdroje, Poland, September 1-5, 2002.
4. HYDRO2002: Conference on Hydraulics, Water Resources and Ocean Engineering, IIT Bombay. Mumbai, December 16-17, 2002.
5. 30th Conference on Fluid Mechanics and Fluid Power, National Institute of Technology Karnataka, Surathkal, December 11-13, 2003.
6. 5th International Conference on Special Functions and their Applications, Lucknow, February 8-10, 2004 organized by the Society for Special Functions and their Applications.
7. International Conference on Mathematical Fluid Dynamics, organized by University of Hyderabad, Hyderabad, December 2-7, 2004.
8. 70th Annual Conference of Indian Mathematical Society, Jodhpur, December 26-29, 2004 organized by Jai Narayan Vyas University, Jodhpur, India.
9. Regional Seminar on Mathematics, Dibrugarh, January 10, 2005, organized by Dibrugarh University, Dibrugarh, Assam, India.
10. International Conference on Environmental Fluid Mechanics, March 3-5, 2005 organized by Indian Institute of Technology Guwahati, India.
11. SANUM2006: Annual Congress of South African Society for Numerical and Applied Mathematics, University of Stellenbosch, Stellenbosch, South Africa, April 3-5, 2006.
12. International Conference on Applications of Fluid Mechanics in Industry and Environment, Indian Statistical Institute, Kolkata, August 28-31, 2006.
13. GLADE2008, University of Auckland, Auckland, New Zealand, July 14-18, 2008.
14. International Colloquium on Perspectives in Fundamental Research, Tata Institute of Fundamental Research, Mumbai, March 2-6, 2010.
15. 8th AIMS International Conference on Dynamical Systems, Differential Equations and Applications, Dresden University of Technology, Germany, May 25-28, 2010.
16. International Congress of Mathematicians, Hyderabad, August 19-27, 2010.
17. International Conference on Mathematical Sciences 2 (ICMS2), Universiti Kebaangsan Malaysia, Kuala Lumpur, Malaysia, November 30-December 2, 2010.
18. 76th Annual Conference of Indian Mathematical Society, SV National Institute of Technology, Surat, India, December 27-30, 2010.
19. 7th East Asia SIAM Conference, Waseda University, Kitakyushu Campus, Fukuoka, Japan, June 27-29, 2011.
20. North East Regional Conference on Mathematics Education, IIT Guwahati, November 25-26, 2011.
21. National Seminar on Recent Developments in Natural Sciences, DKD College, Dergaon, Assam, January 20-21, 2012. (as Chairperson)
22. National Seminar on Mathematics: the Need of the Hour, Shillong College, Shillong, Meghalaya, December 7-8, 2012.
23. National Conference on Frontiers in Analysis and Differential Equations, Bharathidasan University, Tiruchirappalli, December 19-20, 2012.
24. National Seminar on Contemporary Issues in Mathematics and Statistics, Gargaon College, Sivasagar, Assam, March 22-23, 2013.
25. National Seminar on Recent Trends in Mathematics and Applications, Digboi College, Assam, October 7-8, 2013.
26. 10th Annual Conference of East Asia SIAM, Pattaya, Thailand, June 23-25, 2014.
27. 10th American Institute of Mathematical Sciences Conference on Dynamical Systems, Differential Equations and Applications, Madrid, Spain, July 7-11, 2014.
28. 8th International Congress on Industrial and Applied Mathematics (ICIAM), Beijing, China, August 10-14, 2015.
29. National Seminar on Recent Trends of Mathematics and its Applications, Rajiv Gandhi University, Rono Hills, Arunachal Pradesh, November 6-7, 20015.
30. International Conference on Vibration Problems, IIT Guwahati, Guwahati, December 14-17, 2015.
31. 60th Annual Congress of Indian Society of Theoretical and Applied Mechanics, MNIT Jaipur, December 16-19, 2015.
32. Recent Developments in Numerical Techniques and Applications, NIT Patna, Bihar, April 7-8, 2016.
33. International Conference on Applied Mathematics, City University of Hong Kong, May 30-June 2, 2016.
34. The 12th AIMS Conference on Dynamical Systems, Differential Equations and Applications, National Taiwan University, Taipei, Taiwan, July 5-9, 2018.