Abstract This paper presents field results obtained while drilling difficult offshore wells in Azerbaijan and Brazil using a new service that delivers conventional check-shot data while drilling. The operation is similar to a conventional wireline operation in that it uses a surface-deployed source and downhole receiver. The key difference between this service and wireline seismic services is that the receiver is included in the drilling assembly; therefore, drilling does not have to be stopped to take measurements. The first case study presents results from the A-1 deviated wildcat well in the South Caspian Sea, where the service was used to reduce depth uncertainty while drilling. The tool delivered real-time check-shot data that were accurate to within 3 ms of a conventional vertical seismic profile (VSP) over the same interval (equivalent to a 10-m depth error at a 4-km depth). In the second case study, seismic data from the B-2 well in Brazil were used to set casing in a narrow window between a fault and the primary reservoir target. The data enabled safe and successful installation of the casing. Both operations were completed with zero rig downtime. Data accuracy was suitable for real-time decisions and eliminated the need to stop drilling to run intermediate wireline VSP surveys. The service offers the industry new options for reducing uncertainty in the well construction process, and it can therefore make a significant impact on cost and safety while drilling a well.