The number of search queries on Google increased to 64.1 percent in March, following 63.9 percent in February and 58.3 percent a year ago, according to Hitwise's report, which based on the surfing habits of 10 million U.S. Web users.
Another survey by online measurement firm comScore Networks showed a lesser increase in Google's U.S. market share, from a 47.5 percent share in January to 48.1 percent in February. Worldwide, comScore estimates Google held a 65.7 percent share of the Web search market.
According to the Hitwise survey, Yahoo search queries in March decreased to about 21.3 percent from 21.5 percent in February, and 22.3 percent in March 2006, while MSN Search dipped to 9.2 percent from 9.3 percent in February and 13.1 percent a year ago.
The Hitwise survey also found that Google is gaining strength in specific categories of searches, such as directing more than 28 percent of traffic to health-related sites in March, and nearly 19 percent of traffic to travel sites.
On Wednesday, Google shares closed at $464.53 on the Nasdaq, and Yahoo closed at $31.17. Both companies will report quarterly financial results next week.