Many questions concerning the function of the cytoskeleton can be addressed using functional antibodies either in in vitro assays or in whole cell systems. Ultimately, the function of a component has to be studied within intact cell systems. A problem, which one has to be overcome, is the delivery of the antibody into the cells. The delivery of antibodies can be a particular problem either, if large numbers of cells will be analyzed or if one wants to study adhesive as well as non-adhesive cells. Several approaches to introduce proteins and other components into cells have been published, such as electroporation (1), scrape loading (2), or delivery via liposomes (3). Among these the most widespread are microinjection and electroporation. While microinjection is routinely used for adhesive cells, this method will be very time consuming when large numbers of cells have to be studied. Also, it is not feasible to employ this technique for small cells in suspension. Electroporation, on the other hand, has been employed successfully to introduce various components in to cells in suspension. Chang (4,5) has also developed an electroporation method for adhesive cells using an oscillating electric field; still a fare number of cells die during this procedure.