The group’s board members, which include some of the more prominent names in the medical marijuana industry, say the need for a national association has become increasingly apparent with the explosion of the legal marijuana business. Such businesses include dispensaries, growing facilities and equipment suppliers.

J. B. Woods, a former insurance agent for Allstate who now sells property and product-liability insurance to medical marijuana businesses in Colorado and other states, is one of the 23 board members. Mr. Woods said the industry had grown so quickly and laws had changed so rapidly that it can be difficult for medical marijuana businesses  and the property owners and banks they deal with  to know if they are operating legally.

“A lot of times these dispensaries can make a huge capital investment only to find out that the local municipality changed its rules, and they have to close down,” he said. “You are in an industry that is very complicated, and ultimately it’s about having a source of credible information.”

The group will officially begin at a national convention in Denver next month.

“This is an industry in its infancy,” said Bob Selan, a board member and chief executive of Kush magazine, a medical marijuana lifestyle publication. “But it is an industry now.”