The establishment of a safety code for walkway surfaces has been materially handicapped by the lack of an ad equate m ethod of measuring slipperiness. The m echanics of walk in g a r elated to slippin g and the design of tes ting in struments are briefl y disc ussed . In order to test floors in actual service a portable slipperin ess tester of the pendulum-impact type was designed a nd construc ted. The design is based on the prem ise t hat, in the process of ordinary wal king, slipping is most likely to occur when the walkway surface is fir s t contacted by t he edge of the hee l. The instrument and test procedure are de cribed . The effects of varying some of t he constants of t he instrument, such as t h e angle of contact between t he te t heel and t he walkway surface, and t he pressure between t he hee l and the walkway, are disc ussed. T ypical resul ts obtain ed with both rubber and leather test heels and und er both dry and wet condi tio ns a re given for various fl ooring and fini shi ng materials.In ge neral, t he t raction furni shed b y dry rubber heels is much better t han that obtain cd with dry leather heels. Man y walkway surfaces are hazardous wh en wet. Good antislip proper ties under wet condi t ions are usuall y a ssociated with rough particles that p roject through t he film of watcr a nd thu p revent it. action a s a lubricant.