Most major offshore industry disasters are often traced to structural failure which could have been prevented if adequate inspections were carried out. To ensure the safe operation of our aging offshore facilities, highly reliable in-service inspection techniques are required to monitor the structural integrity of these facilities. This book x-rays such inspection techniques such as Alternating Current Field Measurement, Long Range Ultrasonics, Digital Radiography, Phased Array, etc. in terms of principle of operation, application, limitations, sensitivity and Probability of Detection (POD) as well as available NDT personnel certification schemes The analysis of these techniques showed high reliability with over 90% probability of detection for minimum defect size of 2mm at 95% confidence level for all the techniques. Such high reliability is required to conduct periodic inspection on our offshore facilities in line with relevant sections of ISO 19902:2007 19902:2007 and DNV-OS-F401:2013 standards for offshore structural integrity assessment.