NEW YORK (AP) _ Assets of the nation's 513 money market mutual funds fell $2.24 billion in the latest week to $382.70 billion, the Investment Company Institute said Thursday.

The decline in the seven-day period ended Wednesday followed a $444.9 million decline the previous week, according to the Washington-based mutual fund trade group .

Fund assets hit a record high $392.14 billion in the week ended March 21, 1990.

The institute said that in the latest week, assets of 250 general purpose funds fell $723.9 million to $133.21 billion, assets of 102 broker-dealer funds dropped $1.29 billion to $157.88 billion, and assets of 161 institutional funds declined $222.8 million to $91.61 billion.

The seven-day average yield on money market mutual funds rose in the week ended Tuesday to 7.68 percent from 7.67 percent the previous week, said Donoghue's Money Fund Report, a trade journal based in Holliston, Mass.

The 30-day average yield was unchanged at 7.67 percent, Donoghue's said.

The average maturity of the portfolios held by money funds was 45 days, up from 44 days, Donoghue's said.

The newsletter Bank Rate Monitor said its survey of 100 leading commercial banks, savings and loan associations and savings banks in the nation's 10 largest markets showed the effective annual yield available on money market accounts fell to 6.16 percent as of Wednesday from 6.18 percent a week earlier. The North Palm Beach, Fla.-based newsletter said the effective annual yield available on special savings accounts, called Super NOW accounts, was unchanged at 5.04 percent.

Bank Rate Monitor said the effective annual yield was 7.91 percent on six- month certificates of deposit, unchanged from the previous week. Yields were 8.10 percent on 1-year CDs, unchanged; 8.10 percent on 2 1/2 -year CDs, unchanged; and 8.17 percent on 5-year CDs, unchanged.

809EDT