Objective: To identify trajectories of posttraumatic stress disorder (PTSD) symptoms from before to 2.5 years after deployment and to assess risk factors for symptom fluctuations and late-onset PTSD. Method: 743 soldiers deployed to Afghanistan in 2009 were assessed for PTSD symptoms using the PTSD Checklist (PCL) at 6 occasions from predeployment to 2.5 years postdeployment (study sample = 561). Predeployment vulnerabilities and deployment and postdeployment stressors were also assessed. Results: Six trajectories were identified: a resilient trajectory with low symptom levels across all assessments (78.1%) and 5 trajectories showing symptom fluctuations. These included a trajectory of late onset (5.7%), independently predicted by earlier emotional problems (OR = 5.59; 95% CI, 1.57- 19.89) and predeployment and postdeployment traumas (OR = 1.10; 95% CI, 1.04-1.17 and OR = 1.13; 95% CI, 1.00-1.26). Two trajectories of symptom fluctuations in the low-to-moderate range (7.5% and 4.1%); a trajectory of symptom relief during deployment, but with a drastic increase at the final assessments (2.0%); and a trajectory with mild symptom increase during deployment followed by relief at return (2.7%) were also found. Symptom fluctuation was predicted independently by predeployment risk factors (depression [OR = 1.27; 95% CI, 1.16-1.39], neuroticism [OR = 1.10; 95% CI, 1.00-1.21], and earlier traumas [OR = 1.09; 95% CI, 1.03-1.16]) and deployment-related stressors (danger/injury exposure [OR = 1.20; 95% CI, 1.04-1.40]), but not by postdeployment stressors. Discussion: The results confirm earlier findings of stress response heterogeneity following military deployment and highlight the impact of predeployment, perideployment, and postdeployment risk factors in predicting PTSD symptomatology and late-onset PTSD symptoms.