Currently there are five mobile networks in Pakistan as given below:

Mobilink is on the first place with highest number of subscribers and Telenor takes the second place. Zong is new in this business and is on last but it's subscribers are increasing very fastly. Mobilink and telenor will be no longer on top because ufone is struggling hard to take the first position. 
Reports says that people are leaving mobilink and porting to other networks because mobink is not providing exciting sms packages,cheap calls and not even advertising its products.
If the things go on in this way then Ufone will take the lead.
Many new mobile networks are also trying to introduce their services in Pakistan and will become operational in 2012. 
Pakistan mobile industry is an emerging industry of Pakistan with 90 million subscribers.