Hong Kong
Hong Kong Special Administrative Region -- Xianggang Tebie Xingzhengqu

Fixed line to
Mobile Phone

Mobile Phone to
Fixed line

Mobile Phone to
Mobile Phone

Local Calls: Dial the Mobile Phone prefix ('91' to '99' or '170' to '179')* + remaining four or six digits of local Mobile Phone number.
Example
A call from a fixed line in Hong Kong to a Mobile Phone in Hong Kong:
'91' + remaining six digits of Mobile Phone number

Local Calls:  Dial the local eight-digit number.

Example

A call from a Mobile Phone in Central to a fixed line in Central:
Dial the local eight-digit number

Local Calls:  Dial the Mobile Phone prefix ('91' to '99' or '170' to '179')* + remaining four or six digits of local Mobile Phone number.

Example
A call from a Mobile Phone in Hong Kong to a Mobile Phone in Hong Kong:
'91' + remaining six digits of Mobile Phone number

Long Distance: Dial the Mobile Phone prefix ('91' to '99' or '170' to '179')* + remaining four or six digits of local Mobile Phone number. 
Example
A call from a fixed line in Hong Kong to a cell phone in Kowloon:
'91' + remaining six digits of cell phone number

Long Distance:  Dial the local eight-digit number.

Example

A call from a cell phone in Central to a fixed line in Kowloon: Dial the local eight-digit number

Long Distance: Dial the cell phone prefix ('91' to '99' or '170' to '179')* + remaining four or six digits of local cell phone number.
Example
A call from a cell phone in Hong Kong to a cell phone in Kowloon:
'91' + remaining six digits of cell phone number

International Calls: Dial Hong Kong's IAC + country code of country being dialed + area code (or) cell phone prefix + local cell phone number.**

Example

A call from a fixed line in Hong Kong to a cell phone in San Francisco, USA:
001 + [1] + (415) + local seven-digit cell phone number

International Calls: Dial Hong Kong's IAC + country code of country being dialed + area code (or) cell phone prefix + local number.**

Example

A call from a cell phone in Hong Kong to a fixed line in San Francisco, USA:
001 + [1] + (415) + local seven-digit number

International Calls: Dial Hong Kong's IAC + country code of country being dialed + area code (or) cell phone prefix + local cell phone number.**

Example

A call from a cell phone in Hong Kong to a cell phone in San Francisco, USA:
001 + [1] + (415) + local seven-digit cell phone number

*Note: Different cell phone carriers have different cell phone prefixes. See following list.
**Note: Some countries have a unique dialing sequence for incoming calls to cell phones. Refer to the Cell Phone Dialing Guide for the country you are calling.