IN an exhibition hall at Boston's Park Plaza Hotel, a poster showing a forlorn little girl asks a heart-rending question: ''Have you fed your child today?'' Then it adds a stern reminder: ''Child support. It's the law.''
Elsewhere in the room, T-shirts (''Paternity is in the genes''), DNA tests, and paternity-identification forms attest to a growing problem: getting noncustodial parents to support their children. The presence of 40 exhibitors - part of the annual conference of the National Child Support Enforcement Association - also signals a related fact: Collecting child support is big business.
Just how big is evident in the turnout for this year's meeting - a record 1,200 people, including judges, lawyers, case workers, and advocates. For five days, they gathered to consider laws and state-of-the-art techniques for getting absent parents to pay up.
The Department of Health and Human Services puts the potential for child-support collection at $48 billion a year. But Wayne Doss, president of the National Child Support Enforcement Association, points out that if interest were calculated, the real figure would be two to three times higher. Yet only $14 billion is collected.
No longer merely the province of overworked state agencies, child support is a field increasingly filled with for-profit companies: private collection specialists, biomedical laboratories offering ''parentage testing services,'' and manufacturers of computer software to track parents and record payments. The operative term is high tech.
If collecting offers a boon to private firms, it represents a burden to employers. Under federal law, they must withhold wages of workers owing court-ordered support. At Chrysler Corporation, for instance, 9,000 employees with a total of 11,000 court orders require wage withholding. To complicate the process, they are spread across 37 states.
Mike Goeddeke, manager of Chrysler's corporate payrolls, explains that Chrysler spent three years and more than $1 million to develop a multistate system for withholding. With more than three people working full time to process court orders, each deduction costs the company between $5 and $10.
Despite the expense, the effort is earning rewards for Chrysler. ''From custodial parents and courts we've had nothing but compliments and praise,'' Mr. Goeddeke says.
The real beneficiaries of improved collection methods like these are, of course, children. In Arizona, collections have increased fivefold in three years, from $30 million to $150 million. In Los Angeles County, they have almost doubled.
Still, even the most sophisticated tracking devices and withholding systems fail to address what Mr. Doss sees as the biggest challenge - changing public attitudes about nonpayment. People still tend to regard this as a private family problem, he says, when in fact it is ''an enormous social issue'' that goes beyond the economic costs associated with welfare, Medicare for children, and food stamps.
''Socially it also costs us a lot,'' Doss says. ''Children raised in single-parent homes without regular child-support payments are more likely to become school dropouts and to become involved with the juvenile-justice system and ultimately the criminal-justice system.''
Two goals are under consideration here. First, the task of collecting the payments due. But beyond that straightforward goal, there is the ideal of a concerned father, a loving father, a father who actually wants to pay. Even if such fathers do not constitute the majority, their existence argues against the careless use of pejorative terms like ''deadbeat dad.''
As Michael Pitts, national-policy analyst for the Children's Rights Council in Boston, says, ''We need to stop punishing fathers who want to be involved in their children's lives. Children are always the victim. If visitation is denied, children pay. If money is withheld, children pay.''
And what the children pay cannot be measured in money.