The "riskiest and most volatile" category of high-yield bonds made the highest returns in the first quarter of this year, indicating that investors are embracing more dangerous credit risk in order to earn yield.

Standard & Poor's Ratings Services said in a report yesterday that junk bonds rated triple-C or lower gained 5.63% in the first quarter, more than triple the 1.55% return for the double-B rated category. B-rated bonds returned 3.33% in the first quarter.