Some brokers are wondering whether the market's euphoria about recent transactions by SmarTone Telecommunications Holdings has gone too far.
One investment house has even downgraded the stock.
Goldman Sachs changed its recommendation to market underperform from market perform.
SmarTone shares yesterday ended at $25.80, up 13.9 per cent this week.
'The fundamentals of the Hong Kong cellular market remain very difficult,' Goldman analyst Tim Storey said.
'And the competitive framework remains a significant barrier to success in the near term.' Analysts said SmarTone shares were mainly gaining on the back of Tuesday's announcement of an alliance with United States Internet company Yahoo! to provide content for iSmart, its Internet service.
The stock was also supported by a report that SmarTone planned to buy a share holding in Taiwanese mobile operator Far East Tone.