TERRORIST BOMB ATTACKS IN THE U.S. REACHED THEIR MAXIMUM IN THE 1969-71 PERIOD AND DECLINED THEREAFTER. STATISTICS SHOW THAT BOMBINGS DROPPED TO AN AVERAGE OF 163 INCIDENTS A MONTH IN 1973. JANUARY WAS THE MOST DANGEROUS MONTH AND NOVEMBER THE SAFEST. CERTAIN PARTS OF THE U.S., GENERALLY THE MOUNTAIN AND PACIFIC COAST STATES, ARE MORE PRONE TO THIS TYPE OF VIOLENCE THAN OTHER REGIONS OF THE COUNTRY. FBI DATA ALSO INDICATE THAT BOMBERS ARE LIKELY TO REMAIN PEACEFUL ON FRIDAY AND SUNDAYS AND ARE MOST ACTIVE IN MIDWEEK. NO HARD DATA, HOWEVER, ARE AVAILABLE ON BOMB THREATS. ACCORDING TO PROFESSIONAL ESTIMATES, APPROXIMATELY 400,000 BOMB THREATS WERE MADE IN THE U.S. IN 1972, WITH THE PRIMARY TARGETS BEING BUSINESS ESTABLISHMENTS. ONE SURVEY SHOWED THAT 9 OUT OF 10 MAJOR BUSINESSES HAD BEEN THREATENED WITH BOMBING, MOST RECEIVE MULTIPLE THREATS. MOST OF THESE THREATS NEVER CULMINATE IN REAL BOMBINGS. EVIDENCE SUGGESTS THAT MOST PERSONS WHO ISSUE BOMB THREATS ARE EITHER EMPLOYEES OR CUSTOMERS OF THE BUSINESSES CONCERNED. USUALLY THE MOTIVE IS ONE OF REVENGE. BOMB THREATS ARE NEARLY ALWAYS ISSUED BY TELEPHONE AND OFTEN TURN OUT TO BE INSIDE CALLS. METHODS OF COPING WITH THE THREATS INCLUDE REFUSAL TO EVACUATE THE BUILDING, BUT ALERTING EMPLOYEES THAT A SEARCH IS UNDERWAY; SETTING A TELEPHONE 'TRAP' TO TRACK DOWN THE CALLER; AND USING AUTOMATIC RECORDING EQUIPMENT TO GATHER EVIDENCE. OFTEN, THE APPEARANCE OF INVESTIGATORS CREATES SUFFICIENT COMMOTION AND CONCERN TO INTIMIDATE TERRORISTS FROM FURTHER ACTION. UNOFFICIALLY, MANY POLICE OFFICERS APPROVE OF BUSINESS' TACTICS OF DOWN-PLAYING BOMB THREATS. OFFICIALLY, HOWEVER, POLICE MUST REMIND EXECUTIVES THAT ALTHOUGH BETTER THAN 99 OUT OF 100 THREATS ARE SPURIOUS, EACH MUST BE TREATED AS GENUINE. CHARTS AND FOOTNOTES ARE INCLUDED. (PRG)