Phreg can't be used to analyse intervalcensored data in general. Phreg can handle lefttruncated data as specified by fabie10, but lefttruncated data is not the same as intervalcensoring. Though, If the structure of your data is simple enough, then the interval censored data can be analysed as tied data, which can be analyzed with ties=discrete in phreg. In the very newest version there is this proc iclifetest available, which can anlyse interval-censored data. I haven't tried it, but I don't think it allow fra a random effect. There is also the possibility of using proc nlmixed. There you can specify a any likelyhoodfunction and use the random effects. There is a good example of how to specify a right-censored frailty mdel in the examples in the sas-help section. This method can also be used when data are interval censored. The draw-back of this method is that you need a very detailed knowledge of how your likelihood function is constructed, since you have to specify it yourself. jacob
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