np1: a computer program for dose escalation strategies in phase I clinical trials. The continual reassessment method is a recommended dose escalation design for including patients in phase I clinical trials designed to estimate the maximum tolerated dose. However, for a particular trial, the implementation of these methods requires extensive computer programming. Standard 3 + 3 designs do not require this, but have shown to possess poor statistical properties. np1 is a user friendly computer program which has implemented two continual reassessment methods for simulating and conducting a phase I clinical trial. Several options allow the user to investigate operating characteristics under various scenario.