After the world's largest credit and debit card processor, Visa Inc. (NYSE: V), reported earnings last night, today was its main competitor MasterCard Inc.'s (NYSE: MA) turn to step up to the plate. The company posted quarterly earnings figures that topped analysts' expectations, pushing its shares up 10% in morning trading.

MasterCard reported that its first quarter profit more than doubled to $446.9 million, or $3.38 a share, helped by gains from the sale of its investment in Redecard S.A. in Brazil. The weak dollar and more customers who used their credit and debit cards for purchases also boosted the company's earnings.

Included in MasterCard's earnings was 37 cents a share related to the terminating of a customer business agreement. Excluding that, the credit-card giant posted earnings of $3.01 a share, exceeding analysts' estimates for a profit of $2.00 a share.

MasterCard posted a respectable 29% growth for its first quarter revenue, which climbed to $1.18 billion. During the period, the card processor benefited from higher volume of transactions processed. The company also attributed its revenue gain to currency fluctuations, with the euro and the Brazilian real volatile in relation to the U.S. dollar. Analysts expected the company show lower sales of $1.07 billion in the first quarter, according to Thomson Reuters.

Looking ahead, there is some concern regarding the impact that the weak economy will have on credit card processors like MasterCard. The main fears are tied to consumers who may have to cut their spending, adding pressure on MasterCard's revenue too. However, MasterCard's Chief Executive showed optimism over its further gains, and stated that the company "continues to see growth in the U.S. region despite continued economic uncertainty."

Eliza Popescu is a financial writer for the online investment advisory service Investor's Observer.