The feasibility of depositing metal films from a well-defined beam of positively charged chromium ions has been investigated. The design and development of an ion source suitable for this work are described and problems related to the extraction, focusing and deflection of such an ion beam are considered. It is found that the desired focusing and deflection conditions cannot be achieved in practice because of certain fundamental limitations: (i) A low-energy beam of less than 500 ev is necessary to obtain a deposit and prevent damage to the substrate by sputtering. Thus space-charge effects become predominant, causing spreading of the beam. (ii) A lens system having a very short focal length is necessary to give a high beam convergence angle. This limits the deflection obtainable without loss of definition. (iii) Energy spread within the beam may also contribute to poor focusing. A minimum beam diameter of 0·5 mm has been obtained from an ion beam of energy 230 ev having a current density of 8 μA mm−2. Under these conditions the condensation coefficient was found to be approximately 25%, giving a deposition rate of 100 Å min−1.