The Episcopal Church has more than 2.4 million members in 7,679 congregations in 110 dioceses (and one similar geographic convocation) situated in 15 countries plus the United States.
Source: most recent parochial data, 2005
 
Note on Dioceses, Congregations and Church Structure:

• Dioceses and congregations remain part of the Episcopal Church even when local leaders and/or a number of parishioners opt to leave the denomination as a matter of personal choice.
• Dioceses are created by the General Convention and cannot be dissolved without action of the General Convention in accordance with the provisions of the churchwide constitution and canons. Congregations, likewise, are created by a local diocese and continue within that structure unless otherwise decided by the local bishop in consultation with other elected diocesan leaders.
• Since 2003, some 45 congregations are known to the Episcopal News Service to have experienced the vote of a majority of members to consider affiliating with part of an overseas Anglican Province. In many of these cases, an ongoing – albeit smaller – congregation continues within the Episcopal Church, the local diocese, and with a newly elected vestry. 

Following are links to questions and answers about the 2.4-million member Episcopal Church, part of the 77-million-member Anglican Communion that spans 164 countries worldwide. Principal source: An Episcopal Dictionary of the Church by Donald Armentrout.