Question: In recent years I have been pushed into a high enough tax bracket to make municipal bonds attractive. Instead of buying any single issue, I have been considering a municipal bond investment trust sponsored by a group of well-known brokers. I would appreciate your valued judgment as to the safety of these trusts and would also like to know if the broker's charges and annual fees are reasonable.

Answer: I like the municipal investment trusts for people whose tax rate warrants it and who are primarily concerned about regular income.

It is a relatively safe investment. You should review the prospectus for the specific series you're interested in, but most of these trusts limit their portfolios to tax-free bonds rated at least "A" by Standard and Poor's or Moody's, the generally accepted bond rating services.

In this context, "safety" relates to the high probability of the issuers paying interest and principal when due. It does not refer to transient changes in the value of the portfolio.

Like the underlying bonds themselves, the value of the trust units will fluctuate inversely with interest rates in general. But such fluctuations are important only if you redeem the units before maturity. They should not concern you if you expect to continue to hold the units for the income they produce.

In addition to their relative safety, I like the trusts because if you wish you can get a monthly payment rather than the semi-annual interest paid by individual bonds.

And the trust units are registered -- that is, issued specifically in your name -- whereas most tax-free bonds are bearer bonds and require both strict safeguarding and semi-annual coupon-clipping.

Trust expenses are relatively low. The initial sales fee for each of the two most widely distributed trusts is 4.5 percent and 3.75 percent, respectively.

Since the trust is not "managed" and the portfolio is static, annual fees are quite low, as little as $1.50 per $1,000 of assets.

In any case, the yield quoted to a prospective purchaser is net of charges; that is, it is derived by dividing the net interest to be received by the gross investment and already takes all charges and fees into account.

Q: I would appreciate your advice on an investment of $1,000 for my great-great-granddaughter who is 1 year old. I'm thinking of an investment that will extend over a period of 20 years, with the income accumulating.

A: In my opinion the best place to put this $1,000 gift is in a growth-oriented mutual fund.

Funds acquired a bad name during the last decade. This may have been at least partially deserved in the first half of the 1970s. But over the last few years, the fund averages have outperformed the general market averages.

There are hundreds of funds with varying stated objectives. A growth fund is best suited for your needs because its aim is the long-term accumulation of capital. Growth funds generally invest in the common stocks of companies whigh may not pay much current income but which, in the opinion of the fund managers, have good growth potential.

Do a little research before buying; some funds have been doing quite a bit better than others. Of course, past history is no guarantee of future performance, but at least it's an indicator of successful management up to now.

If you're not familiar with mutual funds, write to the Investment Company Insititute at 1775 K St. NW, Washington, D.C. 20006 and ask for a free copy of their explanatory booklet "The Age-Old Question."

They also will send you on request a list of their member companies, including both load and no-load sponsors. If you prefer to limit your search to no-load funds (those with no sales charges) you can get a free membership directory from the No-Load Mutual Fund Association, Valley Forge, Pa. 19481.

Incidentally, I've put my own money where my typewriter is. My wife and I opened accounts in a growth fund for each of our grandchildren (no "great-greats" yet) at birth. Although it doesn't have the same emotional appeal as, say, an expensive hand-quilted satin crib coverlet, it makes more economic sense -- and will last a lot longer.