Ecological Momentary Assessment has been used to investigate a wide range of behaviors and psychiatric conditions. Previous investigations have consistently obtained promising results with high acceptance and compliance rates, and with only minor reactive effects for specific variables. Despite the promise of this methodology for the study of severe psychiatric populations, little is known about its feasibility in samples at risk for suicide. In the present study, four samples at varying risk for suicide completed an Ecological Momentary Assessment study by responding to five electronic assessments per day over a one-week period. Samples included healthy controls (n=13), affective controls (n=21), past suicide attempters (n=20), and recent suicide attempters (n=42). The results demonstrate satisfactory participation rates and high compliance with daily life repeated assessments across all groups. Importantly, negative thoughts or suicidal ideation were not reactive to the duration of the study, indicating that the repeated assessment of such cognitions in daily life have little or no effect on their frequency. The findings provide support for the use of Ecological Momentary Assessment in the study of suicidal ideation and suggest that mobile technologies represent new opportunities for the assessment of high-risk cognitive states experienced by patients in daily life.