Unit investment trusts reached $9.97 billion at the end of October, a 26.2% rise from the same period a year earlier, the Investment Company Institute reported.

An ICI spokesman said that strong performance in the stock market, combined with the growing popularity of three stock portfolios sponsored by Merrill Lynch & Co., helped drive much of the growth in unit investment trusts.

Indeed, assets held in stock trusts totaled $5.96 billion at the end of October, almost double the $3.10 billion held a year earlier.

Most of those stock trust assets were held in three "Select 10" accounts, which invest in the 10 Dow Jones stocks with the highest dividend yields. Those portfolios - sponsored by Merrill Lynch and a consortium of securities firms - held more than $4 billion in assets as of October.

"These trusts have been popular for people with long-term savings goals," said Roberta Hess, a Merrill Lynch vice president for merchandising.

Banks, however, often find unit trusts a tough sell. They are less liquid than mutual funds, and can be difficult to explain to customers, said John McCune, president of Norwest Corp.'s brokerage subsidiary.

"You're locked into owning something for a long time, and things change and you can't do anything about it," Mr. McCune said. "We just have never emphasized them."

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