Led by Healthdyne (#5 this year), Consul (#6), and BRAE (#11), 27 of the 1983 INC. 100 companies graduated to the 1984 listing. Of those, 4 moved up in standing. The other 23 slipped to lower rankings but remain members of an elite club where sales growth over the past five years exceeding 1,400% is more the rule than the exception.

What of the 73 com-panies that failed to qualify this year? Most of them -- 40 to be exact -- continue to achieve spectacular growth, but at less than the blistering pace of 1984's top 100. Twenty-seven. of the companies, in fact, rank among the second 100 fastest-growing publicly held companies. They range from Swanton Corp. (#101), with a five-year sales gain of 778%, to Computer Associates International Inc. (#200), with a 395% jump. In between are other outstanding performers such as C3, CACI, Cullinet Software, M.D.C., and Ventrex Laboratories -- all of whom have more than quintupled their sales in the past five years.

Eighteen other companies saw sales falter in 1983 and therefore were disqualified. Not surprisingly, they include six companies in the petroleum industry. Hardest hit were Hadson Petroleum Corp., whose sales plunged 52% last year to $21.0 million, and Monument Energy Services Inc., an oilfield services outfit whose sales dropped more than 48%, to $20.5 million. Faring best in the sextet of energy companies was Gulf Energy Corp., which held its sales decline to 12%.

Among others experiencing setbacks last year were Intertec Data Systems Corp. and Machine Technology Inc., which recorded sales decreases of 29% and 27%, respectively. Battling lesser downturns, with drops of 6% to 12%, were Sykes Datatronics, Vector Graphic, Lexidata, and Cetus.

Eleven companies from '83's list did not meet another criterion: sales of more than $100,000 but less than $25 million in the base year 1979. That includes Nelson Research & Development Co., a pharmaceutical producer whose '79 sales were only $32,000 (down from $130,000 in '78). In 1983, however, the company's volume exceeded $3.3 million, more than doubling the previous year. Ten others had passed the $25-million mark by 1979 -- Apple Computer, CPT, Cray Research, Dysan, Intergraph, Liz Claiborne, North American Watch, Pengo Industries, Reeves Communications, and Tandem Computers. While all but Pengo Industries Inc. have at least tripled their sales since 1979, the all-time star is clearly Apple Computer Inc. The company not only chalked up a sales gain of 1,953% in the past five years, it also soared from less than $1 million to almost $1 billion in seven years.

Two companies on last year's roster have been acquired by larger companies. Teleco Oilfield Services Inc., a $51.6-million offshore drilling specialist, was recently acquired by Sonat Inc., a $2.7-billion energy giant formerly known as Southern Natural Resources. And last October, Godfather's Pizza Inc. encountered a stock offer it couldn't refuse. In a transaction valued at $308 million, the pizza chain linked up with Chart House Inc., a $382-million operator/franchisor of steak, Mexican, and Burger King restaurants.

Finally, the Class of '83 is not without casualties. From the position of # 18 on last year's list, Chemical Investors Inc. plunged into bankruptcy last June. Once a high flier in the industrial-tape business, following a series of buyouts that included Borden Inc.'s Mystik Tape division, Chemical Investors became mired in mismanagement that led to charges of inventory thefts, improper accounting, and loan violations. More recent is the collapse of Xonics Inc. (#99 last year), a $119-million maker of medical diagnostic equipment. Although the company had been carrying losses for five years, it had counted on new X-ray and tomography units to resuscitate its bottom line. However, run-ins with the Securities and Exchange Commission, a lawsuit over accounting methods, plus overwhelming development costs and interest charges finally prompted management to pull the plug and seek protection under Chapter 11.