When should Communion be distributed under both forms? My pastor said that it should be done regularly only in monasteries and convents.
Perhaps your pastor is expressing concern for the reverence with which Communion should be received or for preserving the understanding that Christ is fully present under both forms. However, he is wrong.
There have been times throughout history where the distribution of Communion has been limited to one form for reasons of practicality or to combat heresy. In the early Church, for example, where the Eucharist was received generally under both kinds on Sundays, Communion under the form of bread alone allowed for daily reception where Mass was not possible. Likewise, beginning in the late 1200s, distribution of Communion under one form only was required in order to combat the heretical teaching of some that reception under both kinds was necessary in order to receive the whole Christ.
By the time of Vatican II, the Council saw no reason not to begin restoring the reception of Communion under both kinds. This was done in stages. In 1970 the Holy See approved for the United States the bishops’ Appendix to the General Instruction for the Dioceses of the United States, which gave permission for Communion under both kinds at weekday Masses (AGI 242:19).
The Holy See extended this permission in 1984 to Sunday Masses in the U.S., when it approved the bishops’ directory, This Holy and Living Sacrifice: Directory for the Celebration and Reception of Communion under Both Kinds. The directory stated that, in addition to weekday Masses, “Communion under both kinds is also permitted at parish and community Masses celebrated on Sundays and holy days of obligation in the dioceses of the United States” (HLS 21).
The only exceptions are in those cases where the size or circumstance of the congregation would not permit reverent reception of the precious blood or when the congregation is so diverse that the priest cannot tell if its members have been sufficiently instructed about receiving Communion under both kinds.
And finally, far from being appropriate only in monasteries and convents, the law states: “Communion under both kinds is to be desired in all celebrations of the Mass, though this is not possible in all cases” (HLS 19).