Investors are the most bearish they have been since last year's third quarter, cutting their exposure to stocks in May for the fourth month in a row, Reuters polls showed on Tuesday.
Concerns about a slowing global economy and nagging worries about Greek and other peripheral euro zone debt also prompted investors to move into bonds and cash.
Surveys of 58 leading investment houses in the United States, Europe ex-UK, Japan and Britain showed global equity holdings at their lowest since August last year. Bonds and cash were at their highest since September.
"Greece's debt problem and a slowdown in the U.S. economy are increasing uncertainty in financial markets globally," said Yoshinori Nagano, a senior strategist at Daiwa Asset Management.
Specifically, equity holdings in an average mixed portfolio dropped to 50.7%, the lowest since August, from 51.3% in April. There has been a steady drop every month since January.
Bond holdings rose to 35.5% from 34.6%, and cash, where investors tend to go when becoming cautious, rose to 5.2% from 5.1%.
Investors have been made wary by signs of sluggishness in the US economy with high petrol prices crimping consumer spending and bad weather helping to push pending home sales to a seven-month low in April among other factors.
There is also some positioning ahead of the US Federal Reserve's ending of its asset-buying quantitative easing programme.
What remains to be seen is whether the economic and debt concerns, and the accompanying sell-off of risk, presage a major reversal or simply are natural caution during a dip in the cycle.
"There's rollover in leading indicators in the global economy so we're starting to see some downgrades for growth expectations and people are getting a little bit defensive," said Johannes Maier, head of asset allocation at Postbank in Frankfurt.
"There's no need for discussion about (a growth) triple dip, but you have to recalibrate your expectations."
U.S. fund managers lowered their exposure to equities for a second consecutive month and raised their allocation to cash on further signs of sluggish economic growth.
Responses from 15 US-based fund management firms showed an average of 61.6% of assets in equities, down from 63.3% a month earlier and 64.9% in March.
Cash exposure, meanwhile, increased to 3% in May from 2.7% in April and 2.5% in March. Bond holdings rose to 30% in May from 29% in April and 27% in March.
European investors outside Britain cut equities for a fourth month in a row. The survey of 17 asset management firms showed a typical balanced portfolio holding 45.5% of equities in May, down from 46.8% in the previous month.
They held 39.5% in bonds compared with 38.6% in April. Cash holdings rose to 8.8% from 8.1%, hitting its highest level in at least a year.
Japanese fund managers raised their stock weighting while reducing cash to a three-month low, suggesting risk appetite is starting to return after the March 11 earthquake.
Fund managers' average weighting for global equities in May rose to a three-month high of 43% from April's 42.6%. It had dipped to 42.4% in March, the lowest since January 1999.
The weighting for bonds recovered to 49.6%, matching the highest level since the survey began in February 1995. Cash positions were cut to 4.5%.
British investors made few changes other than raising their bond holdings to 22.9% over the month, from 22.1% in April. Cash represented 4.4% of the average global balanced investment portfolio in May, virtually unchanged from April. Stock holdings were unchanged at 52.55.
