PURPOSE OF REVIEW: Initial treatment of primary spontaneous pneumothorax poses dilemmas for clinicians as size classification systems and current treatment guidelines differ in their approaches, and underlying evidence is weak. The purpose of this review is to summarize recent evidence and highlight remaining evidence gaps. RECENT FINDINGS: Recent studies confirm significant variation in practice. New evidence suggests that conservative management may be a viable option in a wider range of patients than previously thought (including some large pneumothoraces), with a reported clinical success rate of 79%. New data regarding aspiration report similar treatment success rates and shorter hospitalizations than chest tube drainage; however, methodological issues challenge these findings. There are conflicting data about the prognostic implications of computed tomography-identified pulmonary dystrophia. SUMMARY: Initial management of primary spontaneous pneumothorax is controversial, and there remains little high-quality evidence to guide decision-making. International differences in classification systems and management recommendations make meaningful pooling of clinical trials difficult. This makes a strong case for international agreement about study methodology in order to facilitate meaningful comparisons. Recent evidence suggests that conservative management may be a viable option and argues for its place in much needed randomized trials.