Department of Ele ctric al Enginee ring, University of C olor ado, Boulde r, C olo.(R eceived D eccmber 7, ] 963) Th e Rayleigh d istribu tion is the di stribution of thc sum of a large num be r of coplanar (or t im c) vectors \\'ith r andom. amplitudes alld Ull ifO rlllly distributed phases. As s uch, it is the lim iti ng case of di stributions a~soci at('d II ith 111 0re gl'IlPral v pctor surn s t hat arise i n practical problems. S uch cases arC' til(' folloll' ing: (a) 'I'll(' p hasC' distribu tions of the vec tor tC'rms are not uni fo rm , e.g., in the case of scatt l' ring fro m rough surface'S; (b) One or more vector tcrms predominaLP, their nwan sq uare va lue' not I>l'illg neglig;ble co m pared to th e m ean square valup of Uw SU Ill , c.g., in tJle ea~e of sigl als propagat ed in eil i (,'. ll1<'teor-scatter, and atmosplwrie noi se; (0) Th e numiJer of \'('ctO I' t('r n ' j~ small, ('.g., in rada r ret ur ns from several clo",(' targets; (d) '1'110 Jlumi)('r of vector le l'm o is ilsl'H randolll , e.g., in at mosp her ic t u rbuh'nce, m ekor-scatter and atm ~pl'(' .. ic noise'. The ('('suI ting distributio ns for t hese cases and their deviatio ns from the R ayleig h distr ibution will be co nsidered.