The ICLIFETEST procedure computes nonparametric estimates of the survival functions and examines the equality of the survival functions via statistical tests. PROC ICLIFETEST is intended primarily for handling interval-censored data, whereas the LIFETEST procedure deals exclusively with right-censored data. You can use PROC ICLIFETEST to analyze data that are left-censored, interval-censored, or right-censored. However, if the data to be analyzed contain only exact or right-censored observations, it is recommended that PROC LIFETEST be used because it provides specialized methods for dealing with right-censored data. For more information about PROC ICLIFETEST, see Chapter 49: The ICLIFETEST Procedure.