Alphabet now comes before Apple atop the list of the world's most valuable companies.
Shares of Google's parent company are pulling ahead of Apple in early trading Tuesday.
Alphabet Inc. first took the top spot during Monday's extended session following strong fourth-quarter earnings. Apple Inc.'s iPhone, meanwhile, is suffering its first downturn since it debuted eight years ago.
In the first regular hours of trading, Alphabet shares rose about 4 percent to push the company's market capitalization to about $539 billion. Apple, with investors uneasy about iPhone sales, lost about 1 percent, dropping its market capitalization to a mere $530 billion.