Actively managed exchange-traded funds crossed the $10 billion mark in 2012, according to new research.

Cerulli Associates, Boston, discloses this finding in the February 2013 edition of “The Cerulli Edge: U.S. Monthly Product Trends.” The report covers trends respecting retail mutual funds and ETFs, including assets under management and flows across asset classes.

The report concludes that active ETF assets under management hit $10.5 billion in 2012, the PIMCO Total Return ETF accounting for the largest share by ETF. Other active ETFs collectively accounted for $6.6 billion in assets in 2012.

The latter compares with $5.2 billion, $3 billion and $1.1 billion respectively, in other actively managed ETFs in 2011, 2010 and 2009.

The number of actively managed ETFs in 2012 totaled 51, the report states. Active equity ETFs accounted for 29 of the total, followed by active fixed-income ETFs at 18 and active money market ETFs at 4.

In 2011, the number of active ETFs totaled just 38, up from 32 in 2010, 26 in 2009 and 15 in 2008.

While acknowledging that rising demand for active ETFs among investors, the Cerulli report observes that the market will remain limited in 2013 because just 29 percent of average advisor portfolios are allocated to passive investments.

“If ETFs are someday going to challenge mutual funds as the dominant investment vehicle, active funds will likely need to gain a foothold,” the report states. “ETFs continue to grow alongside passive investing as a whole, but a breakthrough in the active equity space could unleash a new wave of product development and growth, driving assets at a greater pace than prior years.”

In 2012, active ETF net flows reached $4.9 billion, of which the PIMCO Total Return ETF accounted for $1.2 billion. By comparison, non-PIMCO active ETFs in 2011, 2010 and 2009 attained $2.4 billion, $1.8 billion and $784 million, respectively.