Parenterally administered cladribine (2-chloro-2'-deoxyadenosine) has demonstrated promising efficacy and safety in clinical trials in patients with multiple sclerosis (MS). An oral formulation of this small molecule would be an attractive option for patients. Here, we describe the chemical characterisation of the inclusion complex between cladribine and the drug carrier molecule 2-hydroxypropyl-beta-cyclodextrin (2-HP-beta-CD). Several techniques were used to analyse the complex both in solution and in the solid state. These analyses provided evidence that the inclusion complex cannot be simply reduced to the sum of the two species, as it shows behaviour different from that of the physical mixture of the two components. Furthermore, solution nuclear magnetic resonance spectroscopy demonstrated the existence of an inclusion complex between cladribine and 2-HP-beta-CD. Importantly, analysis of a tablet formulation demonstrated that the chemical characteristics of the inclusion complex are not affected by the manufacturing process, and that the complex is stable during storage. This tablet formulation is currently under investigation for the treatment of patients with MS.