(FORTUNE Small Business) – It's not that you're a procrastinator. And it's not that you're disorganized. No, the reason you're within spitting distance of age 50 and have a nest egg the size of a jellybean can be pinned to the sliding stock market and one other simple fact: Most retirement plans are pathetically unsuited to business owners. How many entrepreneurs do you know with a predictable, ever-rising income that can feed a retirement plan for, oh, say, 35 or 40 years?

We don't know many either. So how do you build a reliable plan for yourself and your company? We have identified at least two strategies that may keep you from working too hard to make ends meet during your retirement.

First, consider an "owner-only 401(k)." Thanks to the Economic Growth and Tax Relief Reconciliation Act of 2001, owner-only 401(k)s have several new advantages over a SEP-IRA or a Simple IRA, among them higher contribution limits. You can now put away $11,000, up from $10,500. Plus, that limit will climb $1,000 a year until 2006, when it hits $15,000 and will be indexed to inflation. Also, employer contributions aren't as hamstrung as they once were by an employee's salary. Now an employer can kick in as much as 25% of after-tax income. Translation: If you're earning $100,000 a year, you could stow away $11,000 as deferred salary and another $25,000 as an employer contribution to the plan, or $36,000 altogether.

For Tom Dermody, a 36-year-old distributor of imported rubber products in LaPorte, Ind., the extra saving power was an important attraction. "I had some health problems that cost me from age 25 to 35, so I didn't have a lot of money to put away. Now I'm trying to play catch-up," he says. If Dermody were 50 or older, he'd be able to add another $1,000 per year to his contributions until 2006, when he would reach the $15,000 limit.

But an extra $1,000 a year isn't going to help a fiftysomething with serious catching up to do. What then? Think back to the days of defined-benefit plans. Remember them? They're what stood behind retirement pensions, back when companies actually gave pensions and gold watches.

A defined-benefit plan guarantees a beneficiary--that's you and your employees--an income in retirement. To make that promise, the company you purchase a plan from tells you how much to save every year, based on actuarial calculations, and does the investing for you. For example, if you're a 55-year-old who wants a $2,000 monthly income starting at age 65, an actuary might say you need to have a lump sum of $400,000 in your account by the time you're 65. The actuary then tells you how much to put in annually to reach that figure. Because investment rates of return will vary from year to year, the amount is likely to change each year.

Unfortunately, there are a couple of potential drawbacks. Unlike an owner-only 401(k), which gives you complete flexibility with your yearly contributions, a defined-benefit plan requires you to make contributions every year for both you and your employees. Also, a defined-benefit plan works well for you only if your employees are all at least ten years younger. On the other hand, there's no limit to how much you can put away--a crucial factor for most business owners. With the right plan--and enough fresh cash--even a jellybean-sized nest egg can grow comfortably large.