Injecting drug users are at risk of and can suffer from serious health problems due to intravenous administration of insoluble particles from street drugs and tablets. Makeshift filters are used to try to remove particles from the injections. The decision to distribute filters from Harm Reduction Centres cannot be based on evidence of efficacy and safety as no such published data exists. The work presented here is part of a larger study which anticipates to provide such evidence. Laboratory methods were developed based on information gathered from drug users. Injections were prepared using drugs of abuse and filtered either through makeshift or commercially available filters. The resulting solutions were assayed for particle size and number (using Coulter Counter®). Comparisons were made with unfiltered injections. The results presented here are from the first part of this study, which investigated the effectiveness of various filters on reducing particulate count and size range of injections made from tablets. The commercially produced filter (Acrodisk®) showed a much greater reduction in particle number and size. This strongly suggests the risks to health could be reduced by the use of such filters. Of the makeshift filters, the Rizla® acetate filter showed the most satisfactory reduction in the number of particles, suggesting their use may be preferable to the currently popular cigarette filter. The ongoing work is looking at the effect of the filtration methods on amount of drug in injections made from tablets and repeating the work using street heroin.