This paper discusses advanced diagnostic features of ultrasonic gas flow meters used for measurement of natural gas which are generally used to assess dynamic meter operation and performance. The basic diagnostic features of most gas ultrasonic flow meters were covered in the companion paper “Ultrasonic Meter Diagnostics – Basics” which covered diagnostics that relate to meter “health” or validation that the meter is operating properly. Advanced diagnostics are typically those that provide operators information regarding flowing conditions that may affect optimum meter performance. These can include determination of installation effects, upstream blockages, dirt or other similar operating conditions that can adversely affect the uncertainty or repeatability of the volumetric flow rate information determined by the flow meter. Most of this information can be generalized to other manufacturer’s transit time ultrasonic flow meters however, these examples provided, particularly with respect to some advanced diagnostic features, are based on the Daniel SeniorSonic ultrasonic flow meter.