We present fast, simple immunoturbidimetric assays suitable for direct determination of antibody 'concentration' and 'functionality' in crude samples, such as in-process samples taken at various stages during antibody purification. Both assays display excellent linearity and analytical recovery. Possible influences from commonly employed buffers and salts (present in samples at various concentrations), and of pH variations, were studied for both assays. Interference effects were shown to be negligible for the 'concentration' assay, such that sample pre-treatment prior to assay is unnecessary. The 'functionality' assay displayed concentration dependent sensitivity to interference for ammonium sulphate and Tris-(hydroxymethyl)-amino-methane, but was essentially unaffected by all other salts and buffer combinations tested. The immunoturbidimetric assays described here are generically applicable to polyclonal antibodies, require only basic laboratory equipment, are robust, fast, cheap, easy to perform, and readily adapted to automation.