Rapid bioassay is very important for immediate and near-term consequence management, which includes identifying contaminated individuals and providing necessary medical intervention during a radiological or nuclear emergency. This paper reports the application of a newly developed bioassay technique for (90)Sr in urine on a field deployable instrument, the Triathler. Performance of this field technique for sensitivity, accuracy and repeatability is evaluated against bioassay criteria (ANSI N13.30). This field technique offers the following analytical merits: (1) minimum detectable activity of 121 Bq l(-1) when 20 ml of urine is used; (2) relative bias of 11.1 % and relative precision of 3.2 % at the level of 45 Bq per 20 ml of urine and (3) sample turnaround time of less than 1 h. The technique meets the requirements for emergency bioassay when a committed effective dose of 0.5 Sv is used as the action dose threshold for medical intervention. Sample throughput can be significantly improved if this technique is automated.