Three-fourths of Americans believe abortions should be legal, but less than one-third of them support unrestricted abortions.

The survey reveals that attitudes on this issue are closely related to attitudes on the circumstances, the stage of pregnancy and perceptions as to when a fetus becomes a human.

Nationwide, 55 percent say abortions should be legal but only under certain circumstances. Twenty-two per cent hold that abortions should be legal under any circumstances; 19 per cent that abortions should not be legal.

These latest nationwide findings almost mirror those recorded in April 1975, when 54 per cent said certain circumstances, 21 per cent thought abortions should be legal under any circumstances, and 22 per cent would not have allowed them.

Here is a question asked:

Do you think abortions should be legal under any circumstances, legal only under certain circumstances, or illegal in all circumstances? [TABLE OMITTED]

To determine the attitudes of those who would allow abortions under certain circumstances, this group was handed a card listing six of the most commonly cited situations in which abortions take place and asked under which they would allow an abortion in each of the three trimesters of pregnancy.

Here are the results: [TABLE OMITTED]

Although the Roman Catholic Church officially opposes abortion under all circumstances, there has been a significant decline during the last two years in the percentage of Catholics who say abortions should be illegal under all circumstances.

Here's how the views of Catholics and Protestants compare now and how they compared two years ago: [TABLE OMITTED]

The results are based on personal interviews with 1.518 adults, 18 and older, in more than 300 scientifically seleced localities from Dec. 9-12, 1977.