THE PLTS & PAX OF 2 ACFT WERE RETURNING FROM AN ANNUAL PLEASURE TRIP. NEITHER ACFT HAD A GOOD COMM RADIO. SHORTLY AFTER TAKEOFF, THEY ENCTRD FOG. THEY FLEW ABOVE THE WX UNTIL THEY WERE NEAR THEIR 1ST REFUELING STOP (GREENVILLE, AL). BOTH PLTS DSCNDD BENEATH THE OVERCAST THRU BREAKS IN THE CLOUDS TO FIND THE ARPT. ONE PLT MADE HIS WAY TO GREENVILLE UNDER A VARIABLE CEILING; HOWEVER, THE OTHER ACFT DID NOT ARRIVE. LATER, WRECKAGE OF N10521 WAS FND ABT 1.5 MI NORTH OF MCGOWIN AIRSTRIP. THE STRIP WAS ABOUT 11 MI SOUTH OF THE PLANNED REFUELING STOP. AN EXAM REVEALED THE ACFT HAD HIT TREES WHILE FLYING ALONG A HIWAY & PWR LINE TOWARD THE AIRSTRIP. NO PREIMPACT MECH PROBLEM WAS FND. THE AIRSTRIP OWNER HAD SEEN AN ACFT MATCHING THE DESCRIPTION OF N10521 ON A NORTHERLY HDG NEAR THE TIME OF THE ACDNT. HE ESTD THE WX WAS 800 TO 900 FT OVC, VIS 2 MI WITH FOG & INTMT LGT RAIN. TESTS OF THE PLT'S BLOOD WERE MADE AT 2 LABS; 1 SHOWED AN ALCOHOL LVL OF 0.05%;THE OTHER SHOWED AN ALCOHOL LVL OF 0.032%. TESTS OF THE PLT'S VITREOUS HUMOR & URINE BOTH SHOWED ALCOHOL LVLS OF 0.08%.