This document summarizes Pakistan-Iran relations from the Iranian Revolution in 1979 until 2013. It discusses the cultural and religious ties between the two countries dating back to Pakistan's independence in 1947. It then analyzes the relationship during different time periods, including strong ties initially after the revolution, growing divides in the 1990s due to sectarian conflicts and nuclear issues, improved trade under Musharraf in the post-9/11 era, and focus on energy projects under Zardari. The document concludes that sectarianism, diverging Afghan policies, US influence on Pakistan, and ties to Saudi Arabia have been the main causes of divergence between the two countries over time.