Procter & Gamble Co. announced plans yesterday to test-market a line of sanitary napkins, its first venture into the feminine hygiene market since it was forced to recall the Rely tampon three years ago during the toxic-shock-syndrome controversy.

The new product, called Always, will be test-marketed in Minneapolis/St. Paul and the Dakotas. Shipments to wholesalers and stores in those states began yesterday, the company said. Always will be marketed in maxi-pad, mini-pad and panty-liner forms. The company would not say when it might move the new products into national distribution.

The giant consumer-products company said that Always, which is made of a different mixture of ingredients than the Rely tampon, had been under development before the Rely controversy.

Rely tampons were pulled off the market in 1980 after it was charged that they caused toxic-shock syndrome, which sometimes leads to death. The company has continued to deny that the product was unsafe. The Rely episode cost P&G well over $75 million.

A P&G spokeswoman said yesterday that, in spite of the Rely controversy, the company's tests show that consumers would bear no particular grudge against a new P&G entry into the feminine-hygiene market.

When Procter & Gamble introduced Rely in 1974, it revolutionized the tampon industry because of its super-absorbency, and it quickly carved out a large share of the feminine-hygiene market. But when incidences of toxic-shock syndrome--which has symptoms including fever, lowered blood pressure and a severe rash--increased dramatically in 1980, investigators quickly pinpointed one of the causes as the Rely tampon, although the illness is not limited to women.

Rely was the only tampon directly implicated in the controversy, and the only super-absorbent tampon that had to be withdrawn from the market. It never has been determined just why the Rely tampon might have been associated with toxic-shock syndrome--some experts theorized that the illness might be related to all super-absorbent tampons. Cases of toxic-shock syndrome still are reported, although not as frequently as before Rely was recalled.

P&G stopped making and selling Rely during the controversy, but maintains that the tampons were not to blame. It is appealing at least one decision against it in a liability suit, fighting other suits, and has settled some legal actions against Rely out of court.