Study design: Case study. Objective: To describe the use of a classification approach in the evaluation and treatment of a pregnant patient with low back pain (LBP). Background: The patient was a 28-year-old primigravida in her 20th week of pregnancy. She presented with a chief complaint of LBP without precipitating trauma. Her pain limited her sitting to 20 minutes or less and restricted her ability to bend forward. Methods and measures: This patient was treated 4 times during a period of 2 weeks. The patient was classified as stage 1 extension syndrome. Because of the patient's pregnancy, treatment with active extension exercises commonly prescribed for this syndrome was deemed inadequate. Therefore, manual joint mobilization was applied to the symptomatic vertebral segment. Additional intervention included moist heat, soft tissue mobilization to the thoracolumbar paraspinals, manual stretching of the hip flexors, abdominal bracing, and wall squat exercises. Results: After 4 treatments, the patient was able to bend forward without pain, sit longer than 1 hour without discomfort, and work with minimal discomfort. She improved from a stage 1 classification to a stage 3 classification. Conclusion: This case illustrates the use of a classification system to guide physical therapy intervention. It also demonstrates an effective and safe use of manual techniques in the treatment of a pregnant patient.