“4° governments and institutions in foreign countries. This is by far the most inexpensive method of sampling fallout, but peculiarities of the collecting surface (Ref. 2) render the samples unsuitable for many desirable quantitative studies. However, the total beta counts, together with certain additional information, have been used in making estimates of gr 90 deposition (Ref. 3). Fig. 2 shows the latest world-wide estimates. Fallout collectors which retain precipitation as well as particulates, while not providing such convenient samples for counting, have been found to collect more radioactivity per unit area than does the gummed film. In fact, it has been found that the bulk of the strontium-90 fallout is brought down by rain and is not retained by gummed film. Thus for direct measurement of the rate of deposition of Sr-90 on a monthly sampling interval high-walled stainless steel pots of about 1 foot diameter have been used (Table 1). The samples _ are transferred to polyethylene bottles and mailed to the Health and Safety Laboratory for analysis. In addition to gr 90 they are analyzed for the shorter- lived isotope sr®89 to show whether the deposited material is of recent origin. These stations are operated through cooperative arrangements with various institutions and governments. The pots are now being replaced with a new collector consisting of a funnel and a simple ion exchange column (Fig. 3) which will simplify and standardize the sample handling procedure (Ref. 4). The so-called "washtub" stations have been established in order to obtain adequate samples over shorter collecting periods for finer-scale studies of fallout rate (Fig. 4), and to obtain more information as to the origin of the precipitated debris by analysis of barium-140, an even shorter-lived radioisotope (Table I), At these stations, collectors of about 5 square,fserATey are exposed continuously and emptied after each rain. HIVES Fig. 4 shows the