About 60 new, high calibre jobs are to be created in Northern Ireland by US investors.
The announcement was made at a business breakfast in Washington DC on Tuesday.
Terex is to create 35 jobs with a £1.7m investment in Dungannon and Dow will establish 25 jobs in Belfast generating almost £1m in salaries a year.
First and Deputy First Ministers Peter Robinson and Martin McGuinness are in the US to encourage investment in NI.
At the business breakfast, they were joined by Darrell Zavitz, vice-president of Business Process Services Center at Dow, and Ronald M DeFeo, chairman and chief executive officer of Terex.
Dow plans to expand its global supply chain by establishing a centre in Belfast and creating 25 skilled jobs.
Mr Robinson said: "There can be no greater endorsement of our world class skills and knowledge base than an investment by a company of this calibre.
"Offering salaries well above the NI private sector average, this is an investment which will deliver quality career opportunities to the people of Northern Ireland and result in a significant, welcome boost to the local economy."
Deputy First Minister Martin McGuinness said: "This investment proves beyond doubt that we can attract international companies, offering quality high-end jobs, even in such challenging times, for the global economy."
Terex is investing £1.7m in its existing operations in Northern Ireland by locating its European Global Business Services Centre in Dungannon, creating 35 skilled jobs.
Enterprise Minister Arlene Foster said: "Terex already has a considerable footprint in Northern Ireland and is a significant employer at its two plants in County Tyrone.
"The decision to also locate its European Business Services Centre in Northern Ireland is an acknowledgement of the value placed on our local capabilities and the support offered by Invest NI."
The announcement was made ahead of a one-day investment conference hosted by US Secretary Hillary Clinton.
Her NI economic envoy Declan Kelly is chairing the conference.
"Dow is one of the largest and best known brands in the world and its new investment in Northern Ireland sends a very positive message to other companies interested in the region," Mr Kelly said.
"Terex has been a long-standing investor in Northern Ireland, and its new investment shows yet again that once a company has experienced Northern Ireland, it will continue to look to the region for continued growth because of all the advantages the region offers investors."
US executives from blue-chip companies are taking part in the conference where they will meet NI business people interested in expanding their US investments.
BBC NI political correspondent Martina Purdy said that despite challenging economic times, there was an air of optimism around the conference.
"It is hoped that, as the US economy recovers, that confidence will lead to long term investment opportunities on both sides of the Atlantic," she said.
In recent weeks, there have been several jobs announcements from US companies investing in Northern Ireland.