The surplus lines business has seen plenty of upheaval during the 30 years since Business Insurance began ranking the market.

While many of the top insurers, brokers and underwriting managers from 1985 survived the horrific underwriting losses and capacity crunch of the mid-1980s, others succumbed to insolvency or runoff or have been transformed by acquisition.

“There is a business life cycle,” said John L. Ward, founder of private equity firm Cincinnatus Partners L.L.C., an insurance private equity firm in Loveland, Ohio. “To see a few changes in the list is not surprising or alarming.”

There are several models of longevity:

• Lexington Insurance Co., a unit of American International Group Inc., remains the largest surplus lines insurer and survived AIG's near-collapse in 2008.

• Admiral Insurance Co. still prospers as a unit of W.R. Berkley Corp.

• United National Insurance Co. remains a top surplus lines insurer, though its parent, Global Indemnity P.L.C. has moved to Ireland.

• Underwriting manager Victor O. Schinnerer & Co. Inc. still operates as a subsidiary of Marsh & McLennan Cos. Inc.

Other top companies from 1985 are still in business but under new ownership:

• Evanston Insurance Co. and its underwriting manager, Shand Morahan & Co. Inc. — formerly affiliates of broker Alexander & Alexander Inc., itself acquired by Aon Corp., now Aon P.L.C., in 1996 — now are subsidiaries of Markel Corp.

• St. Paul Surplus Lines Insurance Co. and its underwriting manager, Atwater McMillian Inc., merged with the rest of The St. Paul Cos. into The Travelers Cos. Inc. in 2004.

• Great Southwest Fire Insurance Co. — a former affiliate of Sentry Insurance a Mutual Co. that wrote an array of surplus lines risks — was acquired in 1986 by United Van Lines Inc., which changed the insurer's name to Vanliner Insurance Co. and shifted its focus to moving company risks. Vanliner has since become a unit of Cincinnati-based American Financial Group Inc.

For several of the 1985 leaders, though, the 1980s and 1990s were not kind: Asbestos and environmental losses, reserve deficiencies and other issues did them in.

• Eighty-three-year-old Mutual Fire, Marine & Inland Insurance Co., the fifth-largest surplus lines insurer in 1985, was the first to go, declared insolvent and ordered into rehabilitation in Pennsylvania in 1986.

• First State Insurance Co., a Hartford Financial Services Group Inc. unit that reported a 357.9% combined ratio in 1984, closed its doors to new and renewal business in 1992. Its underwriting manager, Cameron & Colby Co. Inc., followed suit.

• Crum & Forster Corp.'s International Surplus Lines Insurance Co. and Cigna Corp.'s California Union Insurance Co. similarly went into runoff in the 1990s. International Surplus' business has been under the management of Toronto-based Fairfax Financial Holdings Ltd., which acquired Crum & Forster in 1997; Cigna sold California Union's business along with its other property/casualty runoff operations to Ace Ltd. in 1999.

• Underwriting manager Sayre & Toso Inc. became a casualty when its parent, Mission Insurance Co., collapsed in 1987 in an insolvency so massive it became the subject of a congressional investigation.

Surplus lines brokers, meanwhile, have seen some of the most dizzying changes, swallowed by retail brokers in a wave of industry consolidation in the 1980s and 1990s and then divested amid concerns over potential conflicts of interest raised by then-New York Attorney General Eliot Spitzer in the mid-2000s.

• Crump Cos. Inc. is a case in point. Crump, 1985's third-largest wholesale broker, was bought in 1986 by London-based Sedgwick Group P.L.C. Marsh & McLennan then bought Sedgwick in 1998. In the wake of Mr. Spitzer's charges that combined retail and wholesale operations represented a conflict, Marsh & McLennan sold Crump in 2005 to a private equity firm, which sold it again in 2012 to BB&T Insurance Services Inc. of Winston-Salem, North Carolina.

• Swett & Crawford Group Inc., a St. Paul unit in 1985, was similarly sold in 1997 to Aon, which spun it off to an investor group in 2005.

• Stewart Smith Holdings, the No. 2 broker in 1985, was swallowed up with its parent in 1987 by Willis Faber P.L.C., now Willis Group Holdings P.L.C., which then sold it in 2005 to American Wholesale Insurance Group Inc, now AmWINS Group Inc.

• Cigna sold its Montgomery & Collins unit in 1994 directly to an investor group, which sold some offices in 1999 to retailer Acordia Inc., itself acquired later by Wells Fargo Insurance Services USA Inc.

Surplus lines acquisitions were among private equity investors' first moves into the insurance sector and have become much larger players since then, Mr. Ward said.

Large brokers also may not have lost much with the spinoffs of wholesale units, said John Wicher, principal of insurance investment adviser John Wicher & Associates Inc. in San Francisco.

Brokers have found they can form relationships with independent wholesalers that preserve some revenue without the distractions of ownership and appearances of conflict, he said.

Whether the future holds as many twists and turns for surplus lines companies as the past is an unanswered question.

“The world changes,” Mr. Wicher said.

Check back in 30 years.