IMG News Release - only 1/2 results reported. More to come.IAMGOLD EXPANDS GOLD POTENTIAL ON THE MONSTER LAKE PROJECT, QUEBEC Toronto, Ontario, May 11, 2017 IAMGOLD Corporation (IAMGOLD or the Company) today provided an update on the ongoing exploration program at its Monster Lake joint venture project located 50 kilometres southwest of Chibougamau, Quebec, Canada. The company is reporting assay results from the first eleven drill holes, totaling just over 5,100 metres, from a total of 24 diamond drill holes, totaling 10,657 metres, completed this past winter. The assay results are provided in Table 1 below and include the following highlights: (A drill hole plan map and longitudinal sections are attached to this news release.) Monster Lake Shear Zone, Megane Zone and Annie Shear Zone: Drill hole ML17-190: 4.4 metres grading 5.21 g/t gold o Includes: 1.3 metres grading 15.99 g/t gold and 1.9 metres grading 9.82 g/t gold o Includes: 0.6 metres grading 25.10 g/t gold and 0.6 metres grading 36.90 g/t gold Drill hole ML17-194: 3.1 metres grading 121.67 g/t gold, o Includes: 1.1 metres grading 316.89 g/t gold Lower Shear Zone: Drill hole ML-17-191: 1.8 metres grading 85.27 g/t gold. The 2017 winter drilling program was designed to target high potential areas along the 3-kilometre trend of the Monster Lake Structural Corridor (MLSC) and associated shear zones to improve confidence and expand known zones of mineralization, including the recently discovered second zone located 200 to 400 metres to the north of the Megane Zone, as well as mineralization in a parallel lower shear zone. Structural patterns suggest the potential for additional mineralized shoots along this major corridor. The results from hole ML17-190 drilled in the new zone to the north of the Megane Zone confirm previous results in hole ML15-147 that intersected multiple mineralized shears and may indicate an extension of the zone. Two areas of mineralization were also intersected in the Lower Monster Lake Shear Zone in drill holes ML17-184 and 191 which will require further testing. Infill drilling in the Megane Zone positively demonstrated continuity of the very high grade nature of this lens where tested. Further results from this drilling program are pending and will be assessed when they are received, validated and compiled. Craig MacDougall, Senior Vice President, Exploration for IAMGOLD, stated: Assays from this winter drilling program continue to return encouraging results, including those from a new zone along the main hosting structure, as well as from a lower parallel shear zone. The potential for the discovery of additional mineralized shoots is considered favourable. page 2 of 5 Next Steps Once the remaining assay results are in hand, they will be assessed and may lead to an estimation of an initial mineral resource by yearend. Further drilling will be required to evaluate the potential of the new mineralized areas, the timing of which will be dependent on ground conditions to allow the access of drilling equipment. About the Monster Lake Project The Monster Lake project is underlain by Archean volcanic rocks of the Obatogamau Formation and is traversed by an important deformation corridor and associated gold-bearing mineralized structures. Historical drilling and exploration by TomaGold Corporation (TomaGold) have identified a four-kilometre long structural corridor, along which most of the known gold occurrences discovered to date on the property are associated, including the Megane Zone. IAMGOLD holds a 50% interest in the Monster Lake project. Pursuant to an earn-in option agreement with TomaGold amended on October 30, 2015, IAMGOLD holds an option to earn a further 25% undivided interest, for a total 75% undivided interest in the project, should it spend a further C$10.0 million on the project within a seven-year period, beginning January 1, 2015. Should a development decision be made by the joint venture, or should the joint venture declare commercial production, TomaGold would be entitled to a further C$1.0 million payment. IAMGOLD has completed its first year commitment under the terms of the amended option earn in agreement.