Led by senior stalwarts Cray Research, Tandem Computers, and Tomlinson Oil, 50 of the 1981 INC. 100 companies graduated to the 1982 listing. Of those, 19 moved up in ranking and two retained their positions. The other 29 slipped in the rankings but remain members of an elite club where 1,000% sales growth in the past five years is more the rule than the exception.

What of the 50 companies that failed to qualify this year? Eight did not meet the basic criterion: sales of less than $25 million in the base year 1977. In this category are: Acton, DPF, Intermedics, Nike, Nucorp Energy, Petro-Lewis, Prime Computer, and Rolm -- six of which have passed not only the $25-million mark but the $250-million milestone in the past five years.

Twenty-six other 1981 INC. 100 companies grew in the new base period but were off the 590%+ pace of this year's top 100. At least 21 of these clearly rank among the second 100 fastest-growing smaller companies in the United States; including 15 alumni who registered sales gains of more than 400% in the past five years. Pacesetters among the runners-up include Kinder-Care Learning Centers (+579%), CGA Computer Associates (+543%), and Floating Point Systems (+523%).

Twelve companies in last year's ranking closed fiscal 1981 with sales decreases, thus failing to qualify. Notable among those whose 1981 sales tumbled are Chuck Barris Productions, down 91%; Optel, down 48%; and Cobb Resources (last year's leader), off 44%.

The remaining four companies have created headlines representing good news and bad -- mergers, litigation, and bankruptcy. Having relinquished their independence to merge with larger companies, DSI and Delhi International Oil no longer qualify for the INC. 100. DSI merged with Anacomp (an INC. 100 company in 1979-80), and Delhi has been absorbed by CSR Ltd., an Australian conglomerate.

Meanwhile, Data Access Systems is entangled in setbacks that include severe discrepancies in its 1977-81 financial statements, conviction of its former chief executive officer on fraud charges, and default on its loan agreements. At press time, the firm was scrambling to arrange new credit terms, scale back it staff, and forge a comeback.

Finally, the Class of '81 is not without a casualty. Barraged by creditor demands, Pittsburgh -- based FSC Corp. (No. 32 last year) plunged into bankruptcy last August.