Phage therapy is a possible alternative to conventional antibiotics to treat pulmonary infections caused by multidrug resistance (MDR) bacterial strains [1-4], due to its high specificity, low toxicity, capability of auto-dosing and biofilm penetration. However, most research has been confined to liquid presentations using intranasal instillation and nebulization. Therefore, there is an aim to develop efficacious and stable phage powder formulations for easy storage, transport and administration. We have previously demonstrated the suitability of spray drying and spray freeze drying to incorporate phages into inhalable dry powders , and shown the effect of storage humidity on the long term stability of the spray dried phage powders . In the present work, we extend this to investigate the effect of storage temperature and leucine on the long term stability of inhalable powders of two types of Pseudomonas phages, PEV2 and PEV40.