The Dow Jones Industrial Average (DJINDICES:^DJI) has gained 31 points in premarket trading, suggesting a positive start to the stock market today. Global indexes were mixed overnight: Asian shares gained, while European stocks were down about 0.4% as of 8:30 a.m EDT.

Investors will hear from Federal Reserve Chairwoman Janet Yellen, who this morning will speak to Congress about the economy and likely provide some clues on the central bank's thinking about future interest rate hikes. In the meantime, the Dow could be driven by earnings season, as components JPMorgan Chase (NYSE:JPM) and Goldman Sachs (NYSE:GS) both delivered strong second-quarter results this morning.

Goldman CEO Lloyd Blankfein.

Goldman Sachs raked in $2 billion in quarterly profit, translating to EPS of $4.10. That result was an 11% improvement over last year's haul and a full $1.05 above what analysts were expecting. Revenue also rose to $9.1 billion, which was significantly ahead of expectations for a 7% drop. Goldman saw weakness in its institutional client services business, which fell 11% on weak demand for currency and commodity products. However, a spike in revenue from the investing and lending division more than picked up that slack.

CEO Lloyd Blankfein said in a press release that this quarter's results demonstrate the "diversity, strength, and breadth of our global franchise." Investors seem to agree and had bid up Goldman Sachs' stock by 1.5% in premarket trading.

Meanwhile, JPMorgan Chase easily beat expectations for its fiscal second quarter this morning. Profit was $1.46 per share, and revenue came in at $25.3 billion. Both of those figures were down from the year-ago period, but Wall Street analysts were expecting even worse results of $1.29 in profit and $23.7 billion in revenue.

Consistent with other major bank executives this week, CEO Jamie Dimon sounded upbeat about recent trends in the economy. In a press release accompanying the results, Dimon said that "consumers, middle market companies, and corporations are in increasingly good financial shape and the labor market is showing steady improvement." That improvement helped the bank post gains in its consumer banking business, as deposits climbed 9%. Still, weakness in JPMorgan's mortgage and financial-markets products kept overall results lower year over year. The stock was up 2.7% in premarket trading.