The naturally occurring radioisotope >s87<sRb makes a small contribution to the total dose-rate. Assuming an average potassium: rubidium ratio of 200:1 the contribution is estimated at 2.9% of the beta doserate from potassium. The effect will be negligible in quartz inclusion dating because of the strong attenuation of the beta minus emission from >s87<sRb. In fine-grain dating the omission of the >s87<sRb contribution will overestimate the age of a pottery sherd by not more than 2% and this is regarded as of minor importance when the total error in the technique is at least plus or minus 5%. -- AATA